Earlier quoted context omitted.
It is a fair bit, but for any credit or debit card transaction they’re actually taking on the risk of essentially fronting the cost of the transaction. Well really their partnering bank does, but if something happens they’re left covering that cost. They also have to split the profit with their collaborating bank and possibly the credit card companies. Nowadays I suspect the risk isn’t all all that high, or at least…
costco offers payment processing for 1.99% + 25c (vs 2.9 + 30c), so quite a bit cheaper. my point is that it’s entirely possible to offer the same thing for cheaper if your main concern is cost, especially for higher volume merchants, and not optimizing for developer experience https://www.costco.com/merchant-account.html
AFAIK they see themselves as a "premium" processor, not as a cheap one.