Well, even for "cheap" MF backs ("fat pixel" CCD 10-20 years old back), as they are mostly electronics, I wouldn't worry too much about service and repair. There aren't any moving parts.
As for cost, they are probably at their bottom now. Certainly, they will flounder around this low range for a few years instead of dropping 20-30% per year like they were.
OTOH, since I invested in a Flextight scanner (and a couple others), it's true that I can shoot a lot of film even for the low end bottom of the barrel prices of around $3000.