They have seen me before, and they will often give me a little discount or throw some new thing into my bag to try.
Maybe I could get an extra buck or two off, but I have it pretty easy as a software developer working from home.
Farming and selling at farmer's markets is hard work. If I don't get the very best price, I figure that's a little tip for them.
Of course if I were buying in quantity I might see it differently. But for the bit of produce I buy, I'm happy to pay for quality.
And I bet that if I needed a larger quantity, they would offer me a good deal.
Part of negotiating is building relationships.
I'm not disagreeing with you, and I really enjoyed that strange grocery story. Just offering a related perspective.