I would hope that everyone is aware that merchant prices reflect all costs including credit cards. But that is reality since virtually all sales are via CC.
Example: We both go to the same fuel station and buy $100 of fuel. You pay $100. My CC bill reflects $100 and $5 cash back. I pay $95. No other charges.
I associate transaction fees with foreign countries. There are no transaction fees when I use my Visa card to purchase fuel in Canada and I get 5% cash back on fuel purchases in Canada. Amex does charge 2-3% transaction fee in Canada and hence I don't use Amex in Canada.