Technically the merchant is paying the fee, and he perhaps is passing some or all of it to you.
The reason merchants might not pass it all to you if that they get a lot more sales volume when they support credit cards, so they can still be more profitable while paying for some of those fees.
I know I'm going to get hated for saying this, but the businesses that charge extra for credit card use under $10 are trying to extract as much out of you - they're aiming to get the best of both worlds. The price of their goods are still such that they're assuming you'll pay with a card.
At the end of the day a business has several costs. Rent, cost of shipping, utilities, etc. When these go up so do the costs of goods. Credit card fees are no different in that regard. If they hated it that much they wouldn't support credit card payments. They do support it because then know it'll bring in more revenue than without - and will easily pay for itself and more.
The issue is there's a huge disparity in the fees for certain payment methods.
Some cards cost merchants much more than others, but they are contractually forbidden from differentiating their prices based on that. It's anticompetitive. Lots of "buy now pay later" schemes work similarly, when afterpay was (or is) a big thing they charge 7% and forbid the merchant from including that cost in their prices.
If the consumer had to bear the cost of their payment choice, no problem, but the reality is consumers with low fee payments are paying slightly more than they should for everything and those with high fee payments pay less than they should for everything.
The reason merchants don't pass fees onto credit card customers only is that the credit card network prohibits them from doing so. If they were to charge a credit card fee, they'd get banned from processing credit cards at all.
The reason merchants might not pass it all to you if that they get a lot more sales volume when they support credit cards, so they can still be more profitable while paying for some of those fees.
I know I'm going to get hated for saying this, but the businesses that charge extra for credit card use under $10 are trying to extract as much out of you - they're aiming to get the best of both worlds. The price of their goods are still such that they're assuming you'll pay with a card.
At the end of the day a business has several costs. Rent, cost of shipping, utilities, etc. When these go up so do the costs of goods. Credit card fees are no different in that regard. If they hated it that much they wouldn't support credit card payments. They do support it because then know it'll bring in more revenue than without - and will easily pay for itself and more.