[almost_usual]

I remember reading somewhere the average swipe fee is 1.6% for cards. Don't know how accurate that is but I'm assuming it's not far off.

[Firehed]

You're pretty close to the mark - at least for a company doing that much payment volume. Maybe closer to 1.8% or so. There's dozens of variables (debit vs credit, issuing bank, network, international, chargeback rates, etc...) so it's hard to say with any reasonable degree of certainty.

[kul]

There's a higher fee for "Card not present" transactions.

[jonknee]

Square is card present though.