well, it's totally unlike me, but i entirely forgot to pay by credit card bill last month. it was a big one, too. but, i got on the phone to my credit card company and asked that they waive the late fee, which they were happy to do. sometimes, you just have to ask.
of course, i don't know that they view me as a great customer -- i always (okay, not this time), pay my balance on time and in full. so, they're really not making any money off of me in terms of finance charges or late fees, but they always do get a small percentage of the cost of the goods that i am buying. this percentage is actually paid by the retailer and in the early days of credit, you would often see discounts when you were paying by cash versus credit. today, it's not really something you hear much about, but you can still get some discounts if you pay with cash -- you just have to ask. try it when buying big ticket items like furniture or other major appliances. i don't know that big retailers want to negotiate, but smaller shops are generally happy to give you a bit of a break when you pay cash.