That's the rate though. For little sessions here and there during your working hours and per-minute billing, I feel like it'll be unusual to do more than say 5

That's the rate though. For little sessions here and there during your working hours and per-minute billing, I feel like it'll be unusual to do more than say 5 hours a week even if you often forget to exit before the "garbage collector" turns it off for you. That gets you into below $1/month territory pretty easily. Disclaimer: I work on Compute Engine but not Cloud Shell.