It might not be impossible to set up, but there are far more webhosts that offer php than rails (and believe it or not, there are plenty of people who are in the market for $2/month webhosting).
So unless your time is really cheap ($2/month, that's, considering a 40 hours week $0.0125/hour), you'd be better off just getting a rails hoster.
No. This feels like it's of pure academical value.