1) There aren't many machine on my must have list left.
2) New machines are too expensive and not worth the price.
3) Assuming less people are buying new machines that drives down the secondary market. I have a nice collection of machines and nothing has come out remotely interesting to me so why sell a good old one.
4) With many botique players going tits-up speculators are probably a little wary.
5) all of the above.
I also was having a discussion with someone at a pinball manufacturer about prices. I said with prices they way they are I'm not buying. His response was where else are you going to buy. I responded all over, just not pinball machines. Literally the current market is driving me out as the value/fun balance is screwed IMO. I just bought about 18k worth of upgrades for my toy car. I'm spending more money than I did on pinball on other cool things.