Traditional merchant accounts don’t expose the cost to the merchant until it settles. If you review the bill, it will list a few rates/amounts for different things that vary by card type. It can vary based on so many factors it’s practically impossible to estimate. The tiers don’t have tier level settings, each card product in that tier can have different amounts.

Stripe and the flat x% + $y are of course popular because of the simplicity and predictability of it.