Using plastic could leave consumers on the hook for a hefty merchant surcharge. New credit card fees begin today under terms of a seven-point-two-billion dollar deal between card companies and businesses. As of today, those merchants can add a fee on top of the purchase price for those paying with credit. Exactly how much the merchant might charge is up to them but it could be up to four-percent of the purchase price. It's expected the number of businesses that will take advantage of the fee will be tiny at first. The fee does not apply to those using a debit card for purchases.