How do you price clothing at flea markets?

Where I live everyone sells clothes at the flea, in Hildago Tx (right across the border from Mexico) the clothes vendors has piles of clothes that cover a 10x20 space. They put down a tarp and pile the up.  They give you a plastic bag like the grocery store puts your grocery in and you fill it up for $2 or $3.  Personally I donate all the clothes I get out of a unit unless it is NWT.