The costs of a credit card transaction can vary widely, from under 1% to even over 50%. It all depends on the circumstances of the consumer and the merchant. At one extreme on has a consumer with a 1% cash back credit card that has a low merchant fee of say 1.64% rate that a large merchant can get for a domestic card present transaction and one has an effective cost well under 1%. I have such a credit card. At the other extreme one has a person with poor credit spending $50 to purchase a prepaid credit card in order to make a $20 purchase online. Add to this the merchant fees for the much riskier card not present transaction and the cost is well over 50%. I have also witnessed this. Bitcoin will have a hard time competing in the first case but will completely blow the second case right out of the water. Bitcoin does not need to become a replacement for fiat or eliminate all fiat transactions, or cause the demise of the USD or EUR to be successful. In fact this is very unlikely. No all Bitcoin needs to do to be successful beyond most of our wildest dreams is pick off those transactions that are currently horribly inefficient, and least profitable, in the fiat system.

Think of lionesses going after a herd of zebra or wolves going after a herd of bison. They pick off the weakest zebra or bison and eat it, they do not need to take down the entire herd.