Even if you were 100% perfectly committed, there would be all sorts of little signals and things that would leak out enough for them to adjust pricing accordingly. The kind of clothes you're wearing, the time of day you're shopping at, your gait, expression, etc.

Even if you were able to perfectly exclude all information about you, it's possible to gather data from the hole that you leave behind. You aren't leaving data behind like a lot of other customers, so that would probably make you either old, or privacy-inclined. You're not buying the same things as an old person, so you're not old, and you can pick it up from there.