Star Wars prices, as with every single tradable item on the face of the planet, is purely driven by supply and demand. The more that want it, the higher the price. Bog standard economics. They aren't making them anymore and, as demand rises, price must also.
It's not just an influx of new collector's though. Although there seems to be an influx of new collectors, I'll bet it's not nearly as high as you think when you take into account those like myself who have collected several times before, quit, then come back. Also, take into account those that just quit and never return.
Further considerations are:
1) Those that should not be named (u-graders). They are actively reducing the supply of carded figures.
2) Hoarder Collectors - Those that find that one of anything (or everything) is not enough. I'll bet there are more than a few here that have multiples of some items and have many examples of rare and desirable items and are buying still more. I don't believe these folks should be judged negatively. At least you know that a) the items will one day return to the market and b) the items will be well cared for whilst in their collections.
3) The purchase of the franchise: Although I initially greeted the purchase of SW by Disney with slight horror, I have to say......it feels right. Goddam I love George L for what he's done, but he lost the plot with the prequels. I may have only seen the trailer for E. VII but I felt like a 7 year old watching ESB for the first time all over again. The fact the sequels are coming will, inevitably, drive prices up; both through the increase in number of collectors and the perceived value of vintage items by existing collectors.
4) Investors - Related to 3 above. In recent years, thanks to the revealed flaws in what was perceived as the invincible fortress that is capitalism (we all remember the financial crash, right?) investors have looked for increasingly diverse areas to invest in. Although this may not be overtly evident in vintage SW collecting, I can guarantee it's happening to a small extent. This will, of course, cause prices to rise for the higher end and rarer products. I've seen it in the US comics market and in military medals, both of which I also collect. These are not after short terms gains but longer terms gains and this is what separates them from 5, below.
5) Speculators - There will be those who are already collecting and those who aren't that fall into this category. These buy purely for short terms gain whether that's buying today and selling tomorrow, next month or next year. Again, this will be linked to 3, above. The hype around the new film will have attracted them and they'll be here for the next 4-5 years at least, depending on how many films and stand alone films come out and how successful they are. You think it's bad now? Just wait until after EVII And Rogue One have been screened. If the hype is good then expect a similar scenario to what has happened with another Disney owned company; Marvel. They have published a schedule of films from now until 2028! This has sent comic prices silly with new issues rocketing in value overnight and some comics being issued with a dozen or more different variant covers. It's insane and dangerous for collector's who are forced to pay the inflated prices. This happened in the 90s with the comic market and it very nearly destroyed the entire market. Marvel very nearly went bust at one point. Valiant comics disappeared and closed down for year, Malibu vanished and Image collapsed in on itself. Most of these have re-emerged from the flames into new glory but are the very same companies at the centre of a renewed and re-invigorated speculation bubble. The collapse will happen again......
6) Inflation - Yes, we've suffered a few years of declining wages and increasing costs, but that (in the UK at least) is beginning to reverse. As we feel wealthier (you do, you know? Even if you don't realize it!) you have more disposable income and you have greater security. As such, prices rise.
I could go on but I think I've bored myself, let alone you. If you've managed to read this far, thanks. Your thoughts are appreciated.