But the idea is to tailor prices to what the individual is willing to pay, compensating perfectly for any willingness to do extravagant spending caused by havin

But the idea is to tailor prices to what the individual is willing to pay, compensating perfectly for any willingness to do extravagant spending caused by having more money, cancelling out its effects so that the buyer gets the same old goods at a new price. The seller isn't undercut by another seller, because the buyer is willing to pay that much. It probably falls apart on that last assumption: rich people aren't really willing to pay proportionately more for goods.