That sounds like one nasty buyer you had.

I  think some of the others have it right- put up your prices.

Two reasons.

1. The main reason-people have this idea that quality is related to price and if they see your item at eg 99c and another, similar, at $6.99, I could almost guarantee they will think the dearer one is stronger, better material, whatever.

2. You won't come across as a desperate seller. That buyer you mentioned. She obviously judged by the price, thought you were lucky to be offloading your stuff to her and should run after her if you wanted the money. Now, if the 6 items had been about $7 each, she probably would not have bid but more importantly, might have thought a $42 purchase worth collecting.