They see so few non-locals there, that ripping off strangers hasn't really developed into a thing. If you see someone else pay whatever for something, you can easily get that same thing for that same price. Otherwise lots of things have a fixed and posted price. Other items can be bargained for. Or you can just ask what the price is, and they'll let you continue on your way without any further discussion if you don't like the price. Then you can ask for the price at another stall selling the same thing, and quickly figure out if you're being quoted a reasonable price or not. I was generally able to buy stuff at prices much lower than I was expecting.