loquitur

"rational people behave in predictable ways" fallacy

That's actually not a fallacy at all. The problem is with presuming consistent rationality. People don't always behave rationally even if they behave mostly rationally. The reason economic models have any validity at all is because most people behave rationally most of the time. Think of it: how could anyone know whether a price is fair or reasonable if they didn't behave rationally?

Another issue is whether rational people could disagree about what the right economic decision is. That in turn rests on what different people value. But in the end it comes down to price - people may be willing to pay more for something they value more. But that doesn't mean people who aren't willing to pay it aren't rational, it only means they place different values on the transaction.