My favorite is the local tax office charges extra for paying online vs going in to the office to pay in person. At first, I thought it was a way to recoup the processing fees as you're obviously paying by card online. The last time I paid in person with a card, that fee was not added on though. So they are charging you extra for not having to pay an employee to process your account.

Until a few years ago merchants were not allowed to charge credit card fees. In that case, online fees make a legally-allowable proxy for credit card surcharges.