I found potos? market quite good for quality(reality)/price: digging into the market you can find some real fabric for a reasonable price. what I cannot understand is how they can sell all (you can count more than a hudred cakes) that creamy cakes in a day ... maybe they're just relying in the freezing climate up there.
What to buy: fabric, wool, and hats!
What to pay: trade a bit
The main market was an interesting one, selling lots of great produce and other assorted food items. It was open well into the evening, which was a pleasant diversion after dark too.
What to buy: Potosi has some of the better chocolate in Bolivia, especially their dark bitter one.