There are processing fees built into the system, so not it's not 0%. As mining rewards drop these may have to rise in compensation.
Most people can't mine, and would have to eat fees.
Further to that, BTC is a terrible step backwards for consumers as chargeback is not there. The cost for amazon to introduce consumer protections like this (that may be required by law in some places) is likely to dwarf credit card fees.
What consumer protections are you talking about? Issuing a refund? I'm pretty sure they could issue a refund if they wanted to.
The transaction fees you are talking about are so much smaller than credit card companies they are basically negligible. Also they keep dropping lower.
Most people can't mine, and would have to eat fees.
Further to that, BTC is a terrible step backwards for consumers as chargeback is not there. The cost for amazon to introduce consumer protections like this (that may be required by law in some places) is likely to dwarf credit card fees.