1.Markets are dangerous
Beware! I'm not saying they are the haven of safety. Even though there are some pickpockets, they are pretty safe (not all of them).However, It is also up to you to be cautious with your personal belongings. You can prevent such negative experiences following advices given here
2. Markets are cheap
They are indeed cheap(er) than shopping malls. Mark the difference : cheap vs cheaper.
Even though, they will surely always come as more profitable for the buyer because of the bargain interaction and many other factors, whether your market is cheap or not depends on how you choose it. Some markets are more expensive because they are closer to rich neigborhoods whereas others (where you will find the same items) are cheaper because they are located in poorer areas. Thus, this is something to consider whenever you are ready to shop at an open-air market.
Another aspect is that in markets, you also have proper shops. Unlike the vendors on the street, they pay more taxes and pay to be there so obviously, they tend to be more expensive.
3. You can't find quality items in markets
This might be true if you don't dig. In my country, my favorite "market-men" used to say : fouillez gagnez, which literally means the better you dig, the more likely you will find extra good stuff. Therefore, unlike malls where everything is given to you and displayed in such a way that makes you want to buy it, here you have to work.
Another argument regarding quality is the fact that most items sold in the market have already been worn by someone. This is partially true. Vendors sell second-hand clothes but usually also have deals with people living in western countries. Because of this, they receive all the clothes that multiple brands (H&M, Zara etc) haven't been able to sell, and those are NEW items!
Any other myth you are aware of? Share with me in the comments :)