Stanlore
Super Freak
The reasons for the immediate price hike is because many people noticed that they can make quick money by reselling popular characters because of demands and people coming in to the hobby late. You can see most of the time the hiked up price don't really sell.
A lot of people see the 1:6 figures are good investments. I doubt this can be true now. The figures are produced in larger numbers these days then limited to 3000 back in the day.
As for reissues. I think the toy companies usually signed off a 1 time deal meaning they can make the certain numbers that they contracted for and that's it. The can't go back to production unless they pay the licensing companies addition fee. This helps with keeping collectibles collectibles. That's how these toys hold their value. But this Hot Toys came up with the idea of "improving" their previous releases and make version 2 or DX versions of the same character.
Bikes... sad to say... newbs like you ARE one of the reasons why the old figures cost so much. Are you looking at your incomplete Avengers collection... and does it haunt you everytime you walk by that it dosent have Hawkeye and Fury? Well.. .there you go..~ Being Human does include irrational impulses.
The other reasons being (what others have mentioned) licensing problems, factory capacity, limited quantities, and greedy scalpers. However, a bit of advice.. depending on what characters you are going after... especially if Marvel, there are figures that they will eventually re-issue.
For example.. Nick Fury.. you missed out on Avengers. Why not wait? Captain America: Winter Soldier and Avengers 2 is coming out. Is Avengers Fury the last we'll see of him? I don't think so..~
Also, to touch up on another reason they don't go back. HT have had quite a few stellar releases. If time never shifted gears, they would be stuck in a loop of producing loop after sold out loop of the same **** over and over. To add to that, LESS people would pre-order and assume to get it on a 2nd re-release, 3rd re-release. If that happened, i think we would still be seeing HT Iron Man 1 figures till 2020, before IM2 figures could even start. oh... IMHO...~