you may be right as to what the credit card company charges, but there has to be a middle man somewhere. Some account that tracks your transactions, money changes hands.. accounts are updated.
Credit card machines are (I think) provided by a bank that provides the service, they in turn charge a fee to use the machine, manage the account, and, i would assume charge you for each transaction unless you meet a certain minimum credit sales per month.
Visa may get 2% (maybe more maybe less) but that's probably nothing compared to what the bank is going to take out of that $1.89 purchase.