I'd argue that, in some sense, their accountability comes from two places: that if they try to enforce a price--as you are claiming that they are actually setti

I'd argue that, in some sense, their accountability comes from two places: that if they try to enforce a price--as you are claiming that they are actually setting the price--that is non-sensical, then people will fleece them by taking advantage of the arbitrage opportunity, and--and I'd argue that this is particularly important as this is part of the narrative of this whole concept--that there are multiple of them and the only thing preventing there from being a lot of onramps are government regulations trying to prevent such: decentralized systems and markets get their trust from having options and backup plans in the case that a bunch of people are (and they always are) corrupt.