The BTC fee, in USD, is in the double digits--and occasionally bumps into the triple digits. Credit card fees, in contrast, are swallowed by the merchant, meaning that effectively they are free to consumers. Moreover, the basic fundamentals of capitalism guarantee that merchants can't simply raise their prices because other merchants can than compete with them on the basis of absolute price.

While I sympathize with the merchants, credit card fees are also miniscule in comparison to the costs of handling paper cash securely, so the ultimate economic case is squarely for accepting credit cards.