what happens if the buyer claims the product was broken or the box shipped was empty?
Does the seller not get his money?
This will be handled on a case by case basis. There is no perfect solution.
Have you thought about putting in some Affiliate ads, might earn a few xtra pennies for you.
There are loads of affiliate sites out there.
Also if you use an ad rotator, you can rotate Banners,.
Tradedoubler offer ad rotaion facilities.
I might put up ads in the future to help cover costs. Is tradedoubler better than Google Adsense?