Credit cards can be a mixed blessing for retailers. While they help promote higher revenue and cement customer loyalty, they also carry significant baggage in the form of costly service charges. In many cases, processing costs reach levels that can obliterate your bottom line. There’s good news on the payment front, though. The Independent Service Organizations that sell credit card accounts are more willing than ever to strike deals favorable to retailers. That’s a direct result of a marketplace affected in fundamental ways by the recent recession.