I am actually surprised they went on as long as they have. The big problem with the IT Jem line and price/availability is that there was the IT club, and there were numerous examples of people buying up Jem dolls to scalp online because they were IT club members and had the advance option to order, rather than them being made available to everyone at the same time. The club has to be joined in January and it costs to do it so yeah. It messed up a lot of distributions and pushed the price of some dolls into crazy world.
The worst release I remember was Regine/Danse/Clash/Video. I was actually super lucky in that I think I got the last Regine anywhere because someone sent me a message saying there was a store in France that still had one and I managed to get her.
I haven't kept up with some of the later releases because I can't justify multiple versions of a doll for an outfit and I have the characters I want (albeit I'd take Graphix if I could afford her xD) but I think that the panic and hype over them pushed the price of some of them up higher than they needed to be.
So I recommend patience, stalking of ebay, and more patience. There are more likely to be Misfits and Stingers around than Jem and Rio because of the quantities produced, but also because some Jem fans are insane people with more money than sense and mostly they buy Jem and Rio...
I managed to put some of mine together fairly cheaply by buying a nude doll and then accessories here and there. I did that with Astral. I still am missing her hat, but it's better than the $300 price...
Edit - one other thing, beware of boxed Rockin Romance Jems. There was a big issue with several of them coming out of factory with some kind of mould in the fabric...I forget the details but she sometimes sells cheaper because of that, worth googling about.