On the topic of angering the customer...
I was looking to buy something out of state. The guy gave me a price. I said let's do it. He said he would call me later in the day. The price went up almost 350 dollars. He noted credit card fees, state sales tax. , shipping. I told him I didn't know he had to charge me his state sales tax, but I'm not an accountant. Once he started talking about the credit card fees I told him we can go old school and I'll mail him a check. I ended up passing on the whole ordeal.
Point of story, if that credit card fee was incorporated in the price and not singled out or mentioned I wouldn't have questioned it. But once he mentioned it, it made me feel like I'm paying his bills for him. Better off just incorporating it in the cost. Just my opine.