In my stable ATM ATM:

My Ti roadie has 20,000+ miles on it. So it is $0.25/mile or so between purchase and upgrades

My Ti gravel grinder bike built last year is already at 5,000 miles on it and counting. It currently is around $1USD/mile and dropping.

Roadie long-since has paid itself off simply in not paying for car parking. My gravel grinder will break even simply on car-parking charges in 14 months.