At our library we’re trying to redesign our member database so that we can easily set the site up for e-commerce. We did a little research a while ago on which services to us and we found that PayPal would cost us the least in the long run – now there’s a handy tool (even though a calculator works just as well) to figure out what your PayPal fees will be. Take a look at the PPCalc. You can use it 2 ways. You can see how much you’ll get if a user pays you X amount – or you can see how much to charge in order for you to get X amount.