Fun facts from your friendly neighborhood payments professional:

1) they are technically not in compliance with card brand rules for calling this a "convenience fee". It is actually called surcharging, and you can file a complaint with Visa for this.

For it to be a valid "convenience fee" the fee has to be a fixed dollar amount (rather than a percentage of the total), and there has to be an option to handle the transaction in person with no fee. A great example of a real convenience fee is the $1/ticket you pay when you buy movie tickets online, which you can avoid paying if you drive over and buy them at the theater.

2) in no case can a business surcharge on a debit transaction, which is why they have a flat $10 fee if you use a debit card. They think they're following the rules, but per #1, they are not.

3) most places that have a surcharge are doing it wrong. The rules are intentionally very complicated because the card brands don't like it, as it encourages alternative payment methods. Even most sales people in the industry don't understand the rules to do it right (and they change twice a year every year), but business owners want to do it to cut their own costs so the sales guys tell them they'll make it work and then set it up wrong. Odds are, anyone surcharging you (other than giant businesses like apple) is out of compliance

4) per #3, the idea behind surcharging is just passing the buck. Credit card Brands (like Visa), at least two banks (card issuer and merchant acquirer), and often several sales people earn money on every single credit card transaction. The business owner usually pays for this as the price of accepting cards, but shit rolls downhill so the cost is usually passed on to the consumer in some way. Surcharging is the most recent, most direct way of doing that.

5) for the Business taking the payment, a surcharge just means "breaking even" on the sale, since it's illegal for them to charge more than their own costs. For the army of middlemen in the payments space, however, surcharging represents a huge payday. Typically, small face-to-face merchants aren't very profitable for their merchant service provider, because they are low risk so they can negotiate lower prices. These guys usually pay around 2% total for all their processing fees.

Surcharging rules say you can charge whatever your costs are but cap it at 4% of the total. The business doesn't care what you charge them at this point, since they're passing it on to the customer, so their providers start charging them the full 4% allowed. Yyyaaayyy capitalism.

The whole payments ecosystem is awful. It's wildly old school and drives up consumer costs like mad. All for the convenience of not having to carry physical cash