can I charge per listing using marketpress

Hi just a quick question. Can I charge per listing using marketpress (so charge for eg $3 for 4 items and $10 for 20 items or $0.50 per item something around these lines) instead of charging for creating a store or taking a cut of each sale. even though I know for anyone to sell on my site they would end up creating a store.

any help would be much appreciated
thank you