A startup processing $50,000 in monthly card payments will hand over roughly $1,750 to payment processors at standard rates. Scale that to $500,000 monthly, and the annual cost climbs past $200,000. The processor you choose determines how much of your revenue stays in your account, how quickly funds settle, and how many customers complete checkout instead of abandoning it.

High-growth startups face a specific problem: the payment infrastructure that works at $10,000 monthly volume becomes expensive or limiting at $1 million. Switching processors mid-growth costs engineering time, creates reconciliation headaches, and risks transaction failures during migration. Picking the right processor early saves money and engineering hours later.

Stripe

Stripe processes $1.4 trillion in annual payment volume, up 38% from 2023. That figure equals roughly 1.3% of global GDP. The company serves half of the Fortune 100 and 62% of Fortune 500 companies.

Pricing Structure

Domestic card transactions cost 2.9% + 30¢. International cards run 3.1% + 30¢, plus a 1.5% cross-border fee. ACH transfers cost 0.8%, capped at $5. There are no monthly fees or setup costs for basic payment processing.

Businesses processing over $100,000 monthly can negotiate custom pricing. High-volume merchants often secure rates as low as 2.2% + 30¢.

Global Coverage

Stripe supports 135+ currencies with automatic conversion to your settlement currency. The platform operates in 46 countries and accepts payments from customers in 195+ countries.

Subscription and Billing

Stripe Billing handles recurring subscriptions, automated invoicing, and recurring payments. The system supports fixed-price subscriptions, tiered plans, and usage-based billing models.

Dispute Handling

As of June 2025, Stripe charges a $15 dispute fee plus a $15 counter fee when contesting chargebacks, bringing the total potential cost to $30 per dispute. The counter fee is refundable if you win. Stripe’s Smart Disputes uses AI to automatically respond to chargebacks with a 30% success fee on recovered amounts

Finix

Finix operates as a direct acquirer processor with connections to American Express, Discover, Mastercard, and Visa. This direct integration removes intermediaries that typically add costs and processing delays.

Pricing Structure

Finix uses interchange-plus pricing. Card-present transactions cost roughly 8 cents plus interchange. Card-not-present transactions run approximately 15 cents plus interchange. The company charges a monthly subscription fee in exchange for passing interchange costs directly to merchants without markup inflation.

The interchange-plus model means you see exactly what the card networks charge and what Finix adds on top. Each transaction includes a detailed breakdown of processing fees.

Volume Thresholds

To offset the monthly subscription, businesses should process at least $5,000 in card payments monthly. Volume discounts become available when processing exceeds $1 million in annual card transactions. Finix does not require long-term contracts to access lower markups.

Additional Features

The platform includes automated underwriting, reconciliation tools, and dispute management through a personalized dashboard. Finix works with high-risk industries including nutraceuticals, CBD, lending, and gambling. There are no extra charges for PCI compliance, setup, or fraud protection tools.

Finix processes payments for businesses across the United States and Canada through a single developer-friendly API that handles payment acceptance, payout management, and merchant onboarding.

Adyen

Adyen provides acquiring services in over 45 markets, supports 150+ currencies, and enables more than 250 payment methods. Companies like Uber, Spotify, and eBay use Adyen for payment processing.

Pricing Structure

Adyen uses Interchange++ pricing, which tracks interchange rates and scheme fees at the transaction level. The company calculates the cost of each payment before it completes. There are no monthly fees, setup fees, integration fees, or closure fees.

Published rates start at $0.13 + 0.60% markup over IC++ for Visa and Mastercard. Negotiated rates can drop to 0.46% + 10¢ per transaction. Merchants processing over $8 million monthly may access markups as low as 0.25% + 10¢ per transaction.

Security Infrastructure

Adyen holds PCI DSS Level 1 certification and has not reported any major public data breaches. The payment process uses tokenization, encryption, and behavioral analytics for real-time fraud detection. The RevenueProtect system incorporates machine learning and AI-based pattern recognition.

Best Use Cases

Adyen works well for medium to large businesses with global operations or plans for international expansion. The platform suits e-commerce, retail, and hospitality sectors where multi-currency support and international payment methods matter.

Square

Square provides hardware and software for businesses with physical retail locations alongside online payment processing.

Pricing Structure

In-person transactions through taps, dips, or swipes cost 2.6% + 15¢. Online transactions run 2.9% + 30¢. Manually entered or card-not-present transactions cost 3.5% + 15¢. Invoices cost 3.3% + 30¢ for cards or 1% with a $1 minimum for ACH transfers.

Square charges the same rate for Visa, Mastercard, Discover, and American Express. The free tier has no monthly subscription costs. PCI compliance and dispute expert assistance come included in the processing rate.

Volume Pricing

Businesses processing over $250,000 annually can request custom pricing through Square Premium.

Hardware Costs

The Square Terminal costs $299 or $27/month financed. The Square Register costs $799 or $39/month.

Ideal Customers

Square suits startups and small businesses with lower transaction volumes that need a straightforward setup. The all-in-one approach combines hardware, software, and payment processing without requiring separate integrations.

PayPal Braintree

Braintree processes over $50 billion annually and handles more than 1 billion transactions per quarter. Large companies including Uber, Spotify, and Adobe use the platform.

Pricing Structure

Standard domestic credit and debit card transactions cost 2.9% + 30¢. There are no monthly or setup fees. PayPal Enterprise Payments does not charge monthly fees, PCI compliance fees, or minimum transaction fees.

Braintree does not add extra fees for accepting PayPal, Venmo, Apple Pay, or Google Pay. High-volume merchants can request volume discounts. Custom flat rates, interchange-plus pricing, and discounted rates are available based on business model and processing volume.

Integration Capabilities

The cloud-based platform provides APIs and SDKs for integration into websites and mobile applications. Braintree supports credit and debit cards, PayPal, and various digital wallets. The platform includes fraud protection tools, PCI compliance, recurring billing, and subscription management.

Ideal Customers

Braintree works well for startups wanting to accept PayPal and Venmo without paying additional fees. The platform scales from startups to large enterprises without requiring processor changes.

Checkout.com

Checkout.com is a London-based financial technology company that serves as payment gateway, acquirer, and processor for enterprise clients in e-commerce, technology, and media sectors. The company achieved profitability in 2024 with 45% revenue growth and targets 30% growth for 2025.

Pricing Structure

Checkout.com uses Interchange++ pricing with no minimums and no required contracts. Pricing depends on transaction volume and history. Fees typically start around 2.9% + 30¢ per transaction, varying by volume, payment method, and region. Enterprise clients receive discounted rates. There are no hidden fees, setup fees, or account maintenance fees.

Global Reach

The platform processes payments in 150+ currencies with domestic coverage in 45+ countries.

Intelligent Acceptance

This AI-driven system adjusts transaction processing methods, data handling, routing, and authentication to improve approval rates and reduce costs. The tool has helped merchants generate over $10 billion in revenue.

Client Base

Checkout.com processes payments for Netflix, Pinterest, Vinted, Temu, Uber Eats, DocuSign, ASOS, Grab, Alipay, Alibaba, Shein, and Sony. In 2025, eBay entered an agreement with Checkout.com for payment infrastructure support.

Stax

Stax uses a subscription-based model that separates the monthly platform fee from per-transaction costs.

Pricing Structure

Stax charges a monthly subscription starting at $99. In exchange, merchants pay interchange costs with 0¢ markup on each transaction. This model benefits high-volume businesses where the monthly fee becomes negligible compared to per-transaction savings.

Break-Even Calculation

At $99/month with no per-transaction markup versus 2.9% + 30¢ flat rate, the subscription model becomes cheaper for businesses processing roughly $20,000 or more monthly. The exact break-even depends on average transaction size and card mix.

Features

The platform includes invoicing, recurring billing, and reporting tools. Stax provides a unified dashboard for tracking payments across channels.

Ideal Customers

Stax suits established startups with predictable, higher monthly volumes who want to minimize per-transaction costs. The subscription fee creates a fixed monthly expense that becomes more economical as volume increases.

How to Choose Based on Growth Stage

Processing Under $50,000 Monthly

Square or Stripe offer straightforward setups with no monthly fees. The flat-rate pricing simplifies financial forecasting when transaction volumes fluctuate.

Processing $50,000 to $500,000 Monthly

Finix or Braintree provide interchange-plus transparency that reveals actual processing costs. Volume-based discounts become accessible in this range.

Processing Over $500,000 Monthly

Finix Adyen, Checkout.com, or Stax deliver the lowest effective rates for high-volume processing. Interchange++ pricing with negotiated markups or subscription models outperform flat-rate structures at scale.

Planning International Expansion

Adyen and Checkout.com offer the broadest currency and market support. Both platforms handle localized payment methods that increase conversion rates in specific regions.

Building Custom Payment Flows

Stripe provides the most extensive API documentation and developer tools. Finix offers similar developer-friendly integration with direct acquirer benefits.

Key Takeaways

The payment processing market reached $66.8 billion in 2024 and continues growing at 11.7% annually through 2034. Choosing a processor that scales with your business avoids costly migrations later.

Interchange-plus and Interchange++ pricing models reveal the true cost of each transaction. Flat-rate pricing simplifies accounting but typically costs more at higher volumes.

For high-growth startups, the processor choice affects engineering resources, international expansion options, and bottom-line margins. The 7 processors covered here each serve different growth patterns, transaction volumes, and business models. Match your current needs and projected 18-month growth to find the right fit.