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TL;DR
Five Cost Layers, Not One
A payment either works or it does not. That is the entire experience from the outside. What the invoice shows you is a single number, and what the customer sees is a confirmation screen. Neither reveals the four or five separate parties that took a cut on the way through.
Every card transaction passes through five distinct fee layers. The pricing model your provider uses does not change which layers exist. It only changes which of them you see itemized [1].
The layers at the top of that table are set by the card networks and move for nobody. The layer at the bottom is the one that determines whether a cross-border transaction costs roughly what a domestic one does, or several times more.
Interchange: The Largest Layer, and Nobody in the Chain Sets It
Interchange is the fee the acquiring bank pays to the cardholder's issuing bank on every card transaction. It is set by Visa and Mastercard through published rate tables, and no party in the payment chain can alter it [2]. It is typically the largest single component of a domestic transaction.
The rate varies by card type, transaction method, and geography. In the EU, consumer card interchange is capped at 0.2% for debit and 0.3% for credit under the Interchange Fee Regulation [3]. In the US, interchange is uncapped and typically runs from 1.0-2.5% depending on the card product. A UK consumer debit card carries roughly 0.2%. A US business rewards card can carry 2.5% [4].
This matters for a reason that has nothing to do with pricing conversations. Interchange is why the same product, sold at the same price, costs a merchant a different amount depending on which card the customer happened to reach for. It is the clearest demonstration that payment cost is a property of the transaction, not of the provider.
What does move interchange is the data attached to the transaction. Sending Level 2 and Level 3 data on B2B payments can qualify a transaction for a lower interchange category. 3D Secure authentication qualifies transactions as lower risk. Prompt settlement avoids downgrade surcharges [2]. These are transaction-level engineering decisions rather than commercial ones, and they are available to any merchant regardless of who processes their payments.
FX Spread: The Layer That Only Exists Across Borders
On domestic transactions, this layer does not exist at all. On cross-border transactions it is frequently the largest one, and it is the only layer that never appears as a line item.
When a customer pays in one currency and the merchant settles in another, a conversion happens somewhere in the chain. The difference between the mid-market reference rate and the rate applied at conversion is the FX spread. It is embedded in the exchange rate rather than charged as a fee, which is why it stays invisible on an invoice even when it is the largest cost in the transaction [4].
The size of that spread is a function of the corridor, not of anyone's generosity. Major pairs like USD/EUR and USD/GBP are deep, heavily traded, and tightly priced. Emerging market pairs are thinner, involve fewer counterparties willing to hold the currency, and price accordingly. Converting into a freely floating, deeply traded currency and converting into a managed, thinly traded one are not the same operation and do not cost the same.
The number of parties touching the money matters as much as the currency pair. A payment that crosses three correspondent banks is priced more than once on the way through. The stablecoin sandwich settlement model exists largely because collapsing that chain removes the intermediate steps that each carry a spread.
Why Cross-Border Costs Structurally More
Every layer in the stack gets more expensive when the transaction crosses a border, and the layers compound.
When the customer's issuing bank sits in a different country from the acquiring bank, the card networks apply higher interchange rates and add cross-border scheme fees. The acquirer carries additional cost for the same transaction. And the FX spread, which was zero domestically, now applies [2].
A transaction that costs roughly 2% domestically can cost several times that cross-border once every layer is accounted for [4]. This is not a pricing failure or a provider being opportunistic. It is what the transaction actually costs to move through the infrastructure it has been routed through.
Which points at where the real lever sits.
Local Acquiring Changes the Transaction, Not the Fee
The most consequential variable in cross-border payment cost is not what any individual layer is priced at. It is whether the transaction is processed as a domestic transaction or a foreign one in the first place.
Local acquiring means processing through an acquiring entity in the customer's own country. The issuing bank then sees a domestic transaction rather than a foreign one. The cross-border interchange premium does not apply, because it is no longer a cross-border transaction. The cross-border scheme fees do not apply. And because settlement happens in local currency, FX conversion moves from the transaction layer to the settlement layer, where it can be handled once in aggregate rather than repeatedly on every individual payment.
The revenue effect is larger than the cost effect, and it is the part most businesses miss. Issuing banks apply stricter fraud scoring to foreign transactions, so cross-border authorization rates run materially below domestic ones. Data across providers shows local acquiring improving cross-border approval rates by 16-20% [6]. On meaningful volume, transactions that were previously being declined and are now approved outweigh any individual fee line by a wide margin.
This is why the cost conversation and the conversion conversation are the same conversation, and why treating payment cost purely as a procurement exercise misses where most of the money actually is.
Flat-Rate and Interchange-Plus: Same Layers, Different Visibility
Both pricing models contain all five layers. The difference is visibility, not total.
Flat-rate pricing bundles everything into a single percentage plus a fixed per-transaction fee. It is predictable and simple to forecast, which for many businesses is worth more than granularity. The trade-off is that a low-interchange EU debit card and a high-interchange US rewards card are billed identically, so the blended rate is doing the work of smoothing the difference.
Interchange-plus pricing separates pass-through interchange from the provider's margin. Each transaction is billed at its actual interchange plus a defined margin. It is less predictable month to month, because the card mix moves, but it makes the underlying structure visible [5].
Neither model is universally better. Flat-rate suits businesses that value forecastability and have a stable card mix. Interchange-plus suits businesses whose card mix skews toward lower-interchange products, where a blended rate would be working against them. The right answer depends on the shape of the transaction base, not on which model is cheaper in the abstract.
For businesses thinking about how a gateway fits a cross-border operation more broadly, including acceptance breadth, authorization performance, and payout capability, our international payment gateway guide covers the wider evaluation.
Sources
[1] Payrails. "Payment Processing Fees: Fixed, Interchange Plus, Interchange++." June 2026. https://www.payrails.com/blog/payment-processing-fees-interchange-plus-vs-flat-rate
[2] Adyen. "Interchange Fees Explained." April 2026. https://www.adyen.com/knowledge-hub/interchange-fees-explained
[3] Interchange Fees EU. "What Are Interchange Fees? Complete EU Guide 2026." March 2026. https://interchangefeeseu.com/blog/what-are-interchange-fees-complete-guide-2026
[4] Airwallex. "Payment Gateway Fees Explained: Costs, Comparisons, and How to Reduce Them." February 2026. https://www.airwallex.com/uk/blog/payment-gateway-fees-explained-costs-comparisons-and-how-to-reduce-them
[5] Shuttle. "How Much Does a Payment Gateway Cost? Fees, Pricing & Hidden Costs." March 2026. https://www.shuttleglobal.com/guides/payment-gateway-cost/
[6] Solidgate. "Authorization Rate Optimization: The 2026 Playbook." April 2026. https://solidgate.com/blog/authorization-rate-optimization/
