Market prices

Ok, can someone explain this games market to me? I go to put something up for sale, let's say the vendor price is 6 gil, when I check to see what others have listed, it is less than 6 gil. Why do people put items up for sale for the vendor price or less? Am I missing something? Don't they lose money doing that? I've tried to figure out why but I just don't get it. I figure I must be doing something wrong, or I just don't understand how this games market works.

Some people are not intelligent?

You are not missing anything.

When you see people selling below vendor buying prices, there's only one thing to do about it - Buy the items and vendor them for a profit. I've probably made about 100k or so buying fish on the market and vendoring them.