> I imagine fare gates are much cheaper than controllers.

German living in Switzerland here: What's even more expensive is delays. It's unthinkable to me how to build a high throughput station with ticket gates. And that's not even considering the need for additional fire egresses etc. involved.

Switzerland is a bit more paper-averse than Germany. 80% of people on the train hold up a QR code on their phone for the employee to scan once aboard, 10% hold up their (credit card sized) travel card for them to RFID scan, and the remaining 10% have a paper ticket.