I have had the exact same idea, ever since I found out about fediverse. It’s just difficult to find ways to trust of the network. Never managed to think of a way for easy self-moderation. Money does bring an insane perversion to try and game the system.
I’m guessing the federation part if done correctly with moderation might bring more trust to the network. Since this is an idea about physical commerce, I’m guessing that having a “store” gps location could be useful for partitioning the network node search priority. Highest chance that you would like to buy from your neighbour and not from across the continent first. Otherwise with the amount of items that will be scanned is nightmare-ish.
Somewhere in the comments there is a mention about dropping crypto as a source of trust. If the store needs trust of a user, it doesn’t sound unreasonable to have your national identity there.
Other source of trust and identity, could be friends. It’s easy to trust direct friends and friend of friend. Knowing that it most likely will have up to 5 jumps, that could be a way to “check” if you are trusted on the network. That does bring the bootstrapping problem