> Mining rewards are incentive to secure the network. Security increases the net welfare of the system.

Only to a point. That's the problem, Bitcoin does not and cannot have a negative feedback cycle. It's got the 50 seatbelts problem. If you keep adding seatbelts at some point you're so far beyond safe that any additional incremental seatbelts are simply waste. If you're already consuming 10x as many resources as anyone can possibly muster to attack the network, then any incremental expenditure is simply waste, not added value, not security.

> If you're including mining rewards in the cost for a bitcoin transaction, you should also includes Wells Fargo's payroll in the costs for a "free" ACH

Wells Fargo provides far, far more services than simply facilitating interbank transfers.

ACHs aren't exactly free but they're close, it's like 3/10th of a cent in volume. Low enough that banks are willing to eat it to keep you as a customer. This is actually enough to cover all the costs associated with operating the network, including payroll, as it operates on a cost recovery basis. Because they're not setting fire to all the world's coal to achieve their security model, and a few server racks at the NACHA just aren't that expensive.