2.1% isn't your whole acquisition cost. You will have to eat the inevitable chargebacks and associated fees too (which is not an issue with Bitcoin).
> You'd have to get below 2% on an ongoing basis
I'm not sure what you mean by this. We've never charged more than 1% for merchant processing and I doubt we ever will.
> with all the fraud/rewards/other stuff cards provide, 2% still seems cheap.
Why would I use my 1% cashback credit card at a trusted merchant when I can get a 2% rebate from the merchant instead? I'm not alone in this thinking, many Americans choose the 'cash price' when pumping gas every day.
You make some good points about cash back and gas, but you can't deny there's value in the extra layer of protection between you and the merchant provided by the credit card. I don't know whether it's worth 1%, but it's not worth zero. BTC payment is more like handing a stack of notes, not payment via card.
That's how transaction costs are so low.
Stripe is an expensive acquirer. I'm working with Heartland and we're getting a hair over 2.1%. I suspect this is going to fall even farther as EMV gains wide acceptance and skimming/other forms of fraud become a thing of the past.
I'll admit, that's a tighter market than I thought (CB exchange) but I'm still having a hard time seeing how those economics work long-term without tons of VC. You'd have to get below 2% on an ongoing basis and with all the fraud/rewards/other stuff cards provide, 2% still seems cheap.