I agree it's imprecise. But I'd argue the de facto fees in the existing system are much higher than 2.5%. The biggest cost are all the transactions that should happen but don't. Most merchants/payment companies block payments from dozens if not hundreds of countries due to fears of fraud.
That's only indirectly related to Bitcoin's use of proof of work, though. While Bitcoin's overall design has advantages and disadvantages w.r.t. security, I don't know why an irreversible version of the current system wouldn't similarly be able to reduce fees without needing to "waste" CPU power computing hashes.
