At markets, you are supposed to haggle for your goods a notable exception is bread: its price is fixed. As a general rule, the real price is about half the price that was first asked. The seller may exaggerate the price when he or she thinks that you are a rich tourist ignorant of the real price. After agreeing on a price, don't walk away without buying, this is considered very rude.
Shops like supermarket and restaurants will typically charge fixed prices. Fresh products and Western-style sit-in restaurants are quite expensive, with it not being uncommon to pay $75 for a dinner per person.