This is a huge pile of uncosted assumptions.

If you take cash it means you have to hold it on site. To be insured you have to demonstrate secure handling for the insurer, which would include security systems and limiting the amount in the safe and register. Which means routine trips to the bank, which also incurs costs.

Like...that could all be true, but the rate merchants tried to ditch ever handling physical money rather suggests the fees were worth it (not to mention all the risk mitigation doesn't cover the increased danger to ones personal safety - walking $5000 to the bank is no fun at all).