accepting Credit Cards

Can you give me a ballpark figuare on the percentage charged by credit card
proccessing companies such as authorize.net? I know for $40/month yahoo
small business service charges 1.75% and im wondering if that is a good deal
or should set up my own shopping cart like OScommerce and use my own credit
card proccessing service? I am not hesitant to set up my own shopping cart
but the toll free support offered by yahoo is tempting. So basically im
wondering if procuring my own webhosting and shopping cart/credit cards is
worth it?

Thanks