That’s where the trouble comes: we have to add one stack after another to the market board, and whenever we get undercutted on prices or we need to make a change we have to edit the prices one by one. Moreover, what if you selling too much stuff? This becomes troublesome.
At the moment I need all my 4 retainers in order to sell the stuff I craft/gather daily, because selling this way makes a lot of space, not only on me retainer, but also on the market board: You can easily find a single retainer selling small stacks of a single items multiple times!
So adding the option for buyers to buy the quantity they need would be a lot more profitable and beneficial to both partys (in my humble opinion).