They don't have to be that specific. They can look at you and the other customers in the store in aggregate, and raise/lower prices accordingly. If you're poor

They don't have to be that specific. They can look at you and the other customers in the store in aggregate, and raise/lower prices accordingly. If you're poor and you're a in store full of millionaires, you'll end up paying millionaire prices, unless it's for an item the millionaires rarely buy.