In shops and food markets, prices are set and non-negotiable (unless buying in large bulk quantity). 

In craft markets, prices can be negotiated, especially if buying more than one item.  Foreigners are always quoted higher prices.  The advantage is that many merchants are selling the same items.  If one merchant acts like they don’t want to negotiate, move on and find a merchant willing to lower the price.  It’s best to remain calm but if they are going to lower the price, it shouldn’t take long to deliberate.