Nancy, my insurance picks up the MRI costs but I thought the price range is approx what lori noted or just less. You can contact the MRI center to get an approx quote. That is the best way to judge what you are up against.
To answer your initial question about MRI's post treatment.... as noted by many, after the 3 yr mark post-radio, the doctor will dictate their protocol for MRI follow ups. In my mind, I am absolutely fine with having head MRI's for the rest of my life as it's, to me, the definative way to confirm no regrowths. I'd rather catch a potential regrowth early than late. Regardless of what kind of AN treatment you have (ie: surgery or radio), we know these boogers, although low in %, can regrow (ie: if a cell is missed during treatment or .....), for me, I'd rather stay on top of the game and keep checking, even if the MRI's are done in intervals of every 3 yrs or whatever. For me, I'd rather play it safe than sorry. I sleep through MRI's, so I have no issue having them done. Just my 2 cents.
Phyl