> Once you account for all the costs relative to them in a given year and divide that number with the number of transactions in that same year, I doubt, given the margins of a given transaction, that a bank can break even on 1 cents transactions

This is a strange argument. Visa's costs, per transaction, are demonstrably lower than Bitcoin's. Specific banks and systems may be more or less efficient. But fundamentally, the trustlessness that is a blockchain's selling point comes at the cost--by definition in proof of work systems--of efficiency.