TANF and SNAP are very different than what I am discussing. That are wealth transfers from general taxes to those in need. Very different than wanking into a public grocery store and seeing different prices based on your income.
Feels like we're splitting hairs a bit here.
I guess im still looking for some limiting principle. Why not just mandate that all goods are sold proportional to income.
There are ways to disentangle the undesirable incentives. The Nordic countries in particular have done a great job of this.