When I went to the market (to buy groceries; there were open markets) in Bucharest, sellers would sometimes try to cheat on me.
When I go to a market in a small place (town, village), the sellers are much more honest.
What’s the difference?
In a big market, there are many sellers and many buyers. If you can’t remember them all, build a connection, and always treat people as being „one in many,” you tend not to care if you cheat or get cheated.
If you have a personal relationship with a seller, it matters whether they are honest.
Thus, if possible, buy from small markets with few sellers who will try to build a relationship with you.
Or buy from a supermarket and have almost zero risk of being cheated.