And that is why we’ve continued to pay about 2.5-3% since the 1980s, despite the fact that every element of the card networks’ technical infrastructure and hence cost structure has radically changed since that time.
A simple way to determine whether “look, the burden of proof is on you to prove this is abusive” is the correct standard is this: try to get precise details on how much the underlying service costs, how much the various types of revenue are shared between card processors, Visa, and issuing banks. You’ll find that it’s almost impossible to get a clear picture of those details without signing an NDA. But if I’m wrong about this, come back to me with it and we’ll discuss how to use it to evaluate whether the fees are reasonable.
(I'm open to the idea that this is a market inefficiency that needs government correction - but you need more than just saying "3%" to prove that)