The most expensive ATM you can use
A single $200 ATM withdrawal in a foreign airport, on the wrong card, can cost $14 in combined FX markup and ATM fee — that's 7% of the principal. Online remittance services are typically 0.4–0.8% because they pass through the mid-market rate and charge only a small fee. The "right" channel for a $200 transfer is the same as for a $20,000 transfer, but the cost matters much more for the small one.
FAQ
Is the "mid-market rate" what I should use for invoicing?
For valuation and accounting, yes — it's the most defensible. For actual settlement, you need to use the rate your bank applies, which is mid + spread + any fees. International contracts usually specify a reference (e.g. "the rate published by the European Central Bank at 14:15 CET on the day before payment") to avoid ambiguity.
Why is the card rate worse than the bank wire?
Because the card network (Visa, Mastercard) charges the issuer a fee, and the issuer often keeps the FX spread on top. The bank wire has fixed costs but a smaller percentage markup. For large transfers, a wire is almost always cheaper. For small one-off purchases abroad, a no-FX-fee card is competitive.
What about crypto as a transfer?
For some corridors, especially cross-border remittance, USDT/USDC routed through a licensed on/off-ramp is now competitive with Wise or Revolut, and faster. It introduces custody, counterparty, and tax-reporting complexity that this tool doesn't model. Treat it as a separate decision, not a default.
Methodology
Mid-market rates are illustrative cross-rates via USD using public reference snapshots. The channel slippage is added as a percentage markup over the mid-market rate, plus any flat fee. Bank wire: 2.5% + $35. Card: 3.0%. ATM: 2.0% + $5. Remittance: 0.5% + $1. The "hidden cost" is the difference between the mid-market-equivalent amount and what the recipient actually receives, expressed in the sending currency. Source: BIS Triennial Survey average FX margin by channel.