[almond]

This number is revenue, but don't forget about cost. Cab drivers only started incurring credit card fees when the city made them start taking cards. I tip more when I use my card than when I pay by cash to help the driver offset the few-dollar fees. It's not a very high-margin business.

[PeterisP]

There shouldn't be any "few-dollar fees". If they are paying more than 3% (i.e., much less than the change in tips) for the card transaction, then they are being robbed blind by the bank and/or corrupt officials.