That's very interesting and surprising (I would have guessed much less than 2.5%), but I don't see how it refutes my point that any currency's value is related to how easily it can be counterfeited. There's probably a threshold or two involved, where the convenience of having simple exchange rates between forms of the same currency compensates for losses to counterfeiting as long as the counterfeit rate is low enough.

I don't think you're actually arguing that I could build a currency that scales beyond a tribal scope out of something that's trivial to copy, but that's the point I'm trying to make. If it's too easy to cheat, people will stop trusting the currency and will use something else; therefore the technology behind the currency does affect its value.