Even with the specialist you are probably looking at a few appts with atleat 3 weeks between them wchich you could pay if off over. The tooth will be fine though if he keeps having it cleaned out and temp filled for the mean time, it is heaps more expensive to have a tooth replaced than it is to hang onto them. I know from experience of my own! I ended up having to have a tooth out, having said that though there is no guarantee that if the tooth has the RCT done that it wont end up needing to come out down the track. My tooth was RCT'd and had a crown on it and everything and after about 3 years of doing all of this i had to have it out but mine was cracked and they were never going to be able to clean it out properly!
He would definately have to have a cornw put on it about 6-12 months after the treatment which will be atleast another $1000. But in saying that there probaly isnt much point in doing the RCT if you arent planning to crown it. Root treated teeth are like dead trees they are brittle from having no blood flow to them etc. The only thing holding them in is the ligaments that attach it to the jaw bone.
I personally think it is worth it though, there is nothing like your own tooth to replace it and you definately notice it when its gone!

God get me talking dental and i go off!! Sorry for the rambling