I've received a number of upgrades very reasonably priced this way. It also helps that airlines would rather sell the seats for small amounts than give away 'free' loyalty upgrades which keeps seats open.
Use a new browser session, use something like Tor that protects you from fingerprinting, poke around on a VPN, try changing your user agent. Don't log into anything. This is the ideal way to shop.
There has been a bit in that direction before, like hotel websites showing higher prices to users of Apple devices, but not individualized prices as far as I know.
This is different. The personal price discrimination is what's new.