> You can't put an item in the store on the shelf and charge every customer what you like. You have to put up a price and adhere to that price regardless of who wants to buy. Anything else is illegal. Or at least should be.

It should be but unfortunately I don't think it is. The main reason store prices are the same for everyone is because it wasn't practical to individualize them without making it clear to purchasers that they are getting screwed. Still, store membership programs / value cards are one way this is being done in a limited way. And some stores are already switching to digital price labels which can be updated instantly so this is going to get a whole lot worse.