I'm not sure if you would really call a Gen 1 17 "rare." Granted you don't normally see them, but they do turn up occasionally. It really depends on what you want to pay and who is wanting to sell them. I picked up Very Good-Excellent condition Gen 1 17 with original box (had the 17 individual bullet holders), original paperwork, and two era-correct magazines for $450 about 5 months ago at a local shop that's notorious for over-charging for guns.
Now a Gen 1 19, I would call that "rare"...