system
A chat on subreddit /r/PoliticalCompassMemes
human
Most of the time the bare minimum is to have a bike lane on the passenger side of the parallel parking lane, like Cambridge Massachusetts 

They’re also bizarrely cheap compared to car roads considering they basically require no maintenance cause at worst you have a few hundred points of weight vs multiple tons
gpt
Road maintenance costs for passenger car traffic is very small. In comparing a paved road used only for passenger cars versus only for bikes you'd likely find similar cost. Temperature/climate damage and age would be the driver of the need to repave, not the wear and tear by the vehicles. 

Heavy trucks are responsible for almost all the road maintenance caused by vehicle traffic, but you can't replace this with bikes. 

It's possible bikes could replace the road damage caused by buses, if more people rode bikes and less buses were needed, but I've never seen data for this.