Japan has tap payments for public transit and restaurants for decades, while simultaneously being very cash driven. Will be interesting to see how the cash meta evolves with different countries and cultures.
Here in Canada, Metro Vancouver implemented a tap payment system with gates for its transit system about ten years ago. They started by generating outrage about fare evaders (the previous system was an "honor" based proof of payment, at least for the train). They claimed to be losing ~3 million $CAD yearly to fare evasion. Then they made a plan to retrofit all the train stations with fare gates, and get new machines…
And you assume the previous system cost $0 annually for maintenance?