I think it is similar to the frustration you'd experience if you told a taxi driver you're running late and they responded "okay, then it costs triple." It's an asshole move. Or if you told the bartender that you're celebrating getting a raise and they responded "okay, then your beer costs two bucks more." Or if there's a medicine that usually just reduces heartburn and costs $20, but you need it to survive, so they increase the cost to 90% of your life savings, just because you'll pay it. I'd say it's super dickish, but also struggle to logically articulate why.
I think that pretty much articulates how people view jacked up prices, especially (but not exclusively) in situations where people are in a tough situation through no fault of there own.
Thus, the garage owner who is known for fleecing out-of-towners who have a breakdown is far more likely to get a local reputation as sort of an asshole rather than a shrewd small businessman.
It does apply in other contexts though. for example, tickets to highly sought after concerts and sporting events are probably not as expensive as they could be. (And one result is profits flow to ticket agencies.) Look how hard it was to get tickets to Hamilton for ages. (Probably still is.) The thinking is that, if you're seen as price gouging because you can, that can work for a while but isn't a great look for a long-term relationship, to say, a band.
Can you get away with it when transactions are very occasional? Sure. But things have a way of coming back to bite you.
Neither is better, they're just different sides of an adversarial relationship. I think maybe the problem (and I don't know if this articulates the point well or not) is making the relationship or transaction adversarial in the first place. Adversaries are assholes to each other, hurting each other to help themselves. Generally that is thought of as bad, and you know, fuck those people.
As a thought experiment, what if we make the cab driver example be about time instead of money. Pretend it benefits cab drivers somehow to make rides take as long as possible. (I say pretend, because in most cases in the real world they would be wasting their own time as well.) So let's say you have to be somewhere at a certain time, but earlier is better. But the driver knows exactly what time you have to be there, and makes the trip take exactly that long, even though he could've gotten you there faster. You can see he's doing subpar work, doing worse for you on purpose to benefit himself.
The more targeted the discrimination, the worse it feels. They're targeting your ability to pay, but also your weaknesses. Imagine highly accurate, pervasive, and real-time user profiling (and sharing of information among big companies), and it's not hard to imagine, in the case of Uber, being charged more the day after your paycheck clears, more if they know your specific flight arrived late, more if they know the car rental companies at the airport have low inventory, more if your selected destination is the hotel at which they know you have a reservation, only being presented with "black car" options if they know you have an upcoming business meeting, etc.
The problem is there is this bell curve thing. Charging rich people more sounds good and redistributory. But the really rich people have more leverage because there are so few other buyers with their purchasing power completing.
End result would probably be like super high income tax with low rate "capital gains" loophole.
Why is "the seller would have given it to me for less" any better than "the buyer would have given me more for it"?