And here is an even more helpful fee calculator where you can plug in different #'s and it will crunch the numbers for you:
http://www.newlifeauctions.com/calc.html
After plugging in some #'s it looks like $500+ BINS would be more like 10% but under $100 items the fees start to jump up to 15-20%. I think if you get a store you could lower this but I've heard you need 200-300 items a month listed to make it worth it...Also you could auction at .01-.99 and save on some of these fees but then you are rolling the dice