> people paying for things at stores is not because everyone has actually agreed on the price.

Yes it is. If a normal commodity item such as bottle of milk was outrageous overpriced in a particular store. I would just go to another store.

As for whether I would pay for something without the threat of violence. I do so everyday. I've walked out of stores by mistake with an item I haven't paid for and gone back into the store and paid for it. I don't like my things being stolen, and thus I don't steal other people's things.

I pay for my eggs from a farm and it is a honour system.