Iran charging a massive toll would also cause a crisis with the gulf states and they aren't going to tolerate it. This is much bigger than Iran vs US, and the idea they hold the cards for such a claim is mostly propaganda.
If that is agreed upon it's going to come with some concessions by Iran which is even less likely.
USA could agree to it because it's not particularly dependent on that fuel supply and therefore would only pay the costs indirectly via market forces, which as the thief-in-chief pointed out, does (the parts he cares about of) their economy no harm as a net petroleum-product exporter, and above all else, they are losing the war.