I did some travels in places where bidets are common, here's my take:
- Egypt - basically a brass pipe targeted at your hole, everyone shitting oh it - no for me
- Italy - standalone, you have to jump over - impractical, takes too much space
- Japan/Korea - toilets from space, heated seat warm, water and dryer - comfy, but you need electricity, and if it fails, expensive
- Finland - a shower attached to the toilet's water intake - just cold water, but it's fine, that's the easiest to install and use
Answer from another: nothing. We also have them in various places, like parking, or highway vignettes - you are not using their facilities, you save them money, so they charge you some extra