You launch your store, make your first ten sales, and feel amazing — until you actually look at the deposit in your bank account. It's less than you expected. Not by a little. By enough to make you open a spreadsheet and start doing math at 11 p.m.
Welcome to the world of ecommerce platform payment processing costs. They're not hidden, exactly, but they're spread across enough line items that most sellers don't see the full picture until money is already gone. Let's fix that.
Why Payment Fees Are More Complicated Than the Headline Rate
Every platform advertises a clean, friendly number. "2.9% + 30¢ per transaction" is practically wallpaper at this point. But that number is rarely the whole story, and the gap between the headline and reality is where a lot of store revenue quietly disappears.
Here's what's actually stacked inside your payment costs:
Interchange fees — set by card networks (Visa, Mastercard, Amex) and paid to the card-issuing bank. These range from roughly 1.15% to 2.4% depending on card type. A premium travel rewards card costs you more to accept than a basic debit card, and you don't get to choose which one your customer pulls out.
Assessment fees — also set by card networks, typically 0.13%–0.15%. Small, but real.
Processor margin — the slice your payment processor keeps on top of interchange and assessments. This is where Stripe, Square, PayPal, and platform-native processors make their money.
Platform transaction fees — this one stings. Some ecommerce platforms charge an additional fee (often 0.5%–2%) on every sale if you don't use their built-in payment processor. Shopify is the most well-known example: if you use a third-party processor on their Basic plan, you pay an extra 2% per transaction on top of whatever your processor charges.
Add those layers together and your effective rate on a $100 sale can easily land between $3.50 and $5.50 — not the $3.20 the headline suggested.
The Four Cost Models You'll Actually Encounter
Not all processors price the same way. Knowing which model a platform uses helps you estimate real costs before you commit.
Flat-rate pricing is the most common for small sellers. You pay the same percentage regardless of card type. Stripe (2.9% + 30¢), Square (2.6% + 10¢ in person), and PayPal (3.49% + 49¢ for standard checkout) all use flat-rate models. Predictable, easy to budget, but you're subsidizing premium card users.
Interchange-plus pricing passes the actual interchange cost through to you and adds a fixed markup (e.g., interchange + 0.3% + 15¢). You pay less when customers use cheap cards. This model usually requires a merchant account and is more common at higher volumes — think $20,000+ per month. Processors like Stripe offer this on their custom pricing tiers.
Subscription/membership pricing charges a flat monthly fee plus a small per-transaction cost. Stax (formerly Fattmerchant) is the textbook example: around $99/month and then interchange + a few cents per transaction. It breaks even around $10,000–$15,000 in monthly volume and saves money above that.
Tiered pricing bundles card types into "qualified," "mid-qualified," and "non-qualified" buckets. It looks simple but is almost always the most expensive model for small sellers. Avoid it when you can.
Platform-Specific Fees: A Honest Side-by-Side
This is where ecommerce platform payment processing costs really diverge. The platform you build on determines which processors you can use and whether you'll pay a penalty for choosing your own.
Shopify — Shopify Payments (powered by Stripe) costs 2.9% + 30¢ on the Basic plan, dropping to 2.6% + 30¢ on Shopify plan and 2.4% + 30¢ on Advanced. Use a third-party processor and you pay an extra 2%, 1%, or 0.5% respectively. If you're doing $5,000/month on Basic with a third-party processor, that 2% penalty is $100/month — $1,200/year — just for not using their native tool.
WooCommerce — No platform transaction fee, ever. You pay only your processor's rates. WooCommerce Payments (also Stripe under the hood) runs 2.9% + 30¢ in the U.S. But you can plug in virtually any processor — Authorize.net, Braintree, PayPal — without penalty. For sellers who already have a negotiated merchant account, this is a meaningful advantage.
BigCommerce — Also charges no additional transaction fees regardless of which processor you use. Their built-in rates through PayPal/Braintree start around 2.59% + 49¢. You have 65+ payment gateway options with no surcharge for using them.
Squarespace — Processes through Stripe or PayPal. Basic Commerce plan: 0% platform transaction fee. Business plan: 3% platform fee on top of processor fees. That 3% is steep — on a $50 order it's $1.50 before Stripe even takes its cut.
Wix — Wix Payments charges 2.9% + 30¢ (U.S.). Third-party processors are available but Wix adds a transaction fee on lower-tier plans. Worth checking the current plan page because these numbers shift.
The pattern is clear: open platforms like WooCommerce and BigCommerce let you shop for the best processor rate. Closed or semi-closed platforms charge you for that freedom.
Three Things You Can Do Today to Lower Your Costs
Enough analysis — here's where you actually save money.
1. Calculate your true effective rate right now. Pull last month's total payment processing fees (not just the processor's fee — include any platform transaction fees) and divide by your total revenue. Multiply by 100. That's your effective rate. Most sellers are surprised to find it's 3.2%–4.5% when they expected something closer to 2.9%. Once you know the real number, you have a baseline to beat.
2. Match your processor to your volume. If you're processing under $5,000/month, flat-rate pricing is probably fine — the simplicity is worth a few basis points. Between $5,000 and $15,000/month, start comparing interchange-plus options. Above $15,000/month, get quotes from at least three processors and ask specifically about interchange-plus or subscription models. A 0.4% improvement at $20,000/month is $960/year back in your pocket.
3. Audit your platform's transaction fee situation. If you're on a platform that charges extra for third-party processors, run the math on switching to their native payment tool — or switching platforms. Sometimes the native processor's rate is genuinely competitive. Other times the platform transaction fee is a tax on your loyalty that you're paying for no good reason.
For example: a seller doing $8,000/month on Shopify Basic with Stripe (third-party) pays the 2% platform fee — $160/month, $1,920/year. Switching to Shopify Payments eliminates that fee. The question is whether Shopify Payments' rate is better or worse than Stripe for their specific card mix. Often it's a wash on the processor rate, meaning the switch is nearly pure savings.
What About International Sales and Currency Conversion?
If any of your customers are outside your home country, processing costs get another layer. Most processors charge a currency conversion fee of 1%–2% on international transactions, on top of standard processing fees. Stripe charges 1.5% for international cards plus an additional 1% for currency conversion if it's required. PayPal's cross-border fees can reach 4.4% + a fixed fee.
If international sales are more than 15%–20% of your revenue, it's worth looking at processors that specialize in cross-border commerce — or at least comparing how each platform handles conversion. Some platforms let you present prices in local currencies and settle in your home currency; others make the customer absorb conversion costs, which can hurt conversion rates.
A quick sanity check: if you're doing $2,000/month in international sales and paying 2% extra in cross-border fees, that's $40/month — $480/year — that a better setup might recover.
Chargebacks and Dispute Fees: The Hidden Tax
One more cost that rarely shows up in platform comparison charts: dispute and chargeback fees. Most processors charge $15–$25 per chargeback, win or lose. Some platforms add their own dispute fee on top.
For most small stores, chargebacks are rare — maybe 0.1%–0.3% of transactions. But in certain niches (digital products, subscription boxes, anything with long shipping times), rates can climb toward 0.5%–1%. At 1% on 200 monthly orders, that's two chargebacks a month, potentially $50 in fees before you've even dealt with the lost inventory.
The fix isn't complicated: clear product descriptions, honest shipping estimates, easy-to-find contact info, and a return policy that's less painful than a chargeback. Customers dispute charges when they feel ignored, not just when they're trying to scam you.
You Have More Control Here Than You Think
Ecommerce platform payment processing costs feel like a fixed cost of doing business, but they're actually one of the more negotiable parts of your stack — especially as you grow. The sellers who pay the least aren't the ones who got lucky; they're the ones who did the math early and made deliberate choices about which platform and processor to pair.
Start with your effective rate. Compare it to what's actually available. Then make one change — just one — and measure the difference over 60 days.
Your next step: open your payment dashboard right now and find last month's total fees. That single number will tell you more than any comparison chart ever could.
You've got this.