The pinball market has not changed... the business strategy of the major manufacturers has changed. For the entire lifetime of this hobby, excepting 2 of the last 3 years the manufacturers had enough product that you could walk into your local distributor and walk out with a new pinball machine... any pinball machine made recently, not just whatever wasn't selling well. When this was the case, a recent used pin was the price of a new pin minus about $500. The only pins selling for a premium are ones that you cannot get new without waiting and it is a "price to get it now". This scarcity was previously only accomplished by limiting the amount of certain pins made. There were only 300 or 400 LEs, and those as "investments" held their value only slightly better than the mass market pins. Now Stern, JJP, and even Spooky have drastically increased the number of LE and CE pins they make to the point of making the designation useless. These trims no longer work as "investment vehicles". If Stern knows LEs will be worth 11k or 12k used, they will jack up the price to get all of that money.
As to the economy killing demand? Have you gone to anyone's house to trade pins? I count myself as extremely well off for my age, but 90% of the houses I go to are larger than mine with huge pinball collections. I think that the home buyer with pinball machines at home generally has alot of disposable income, and as such is on the more "financially secure" side. Location pinball my get hurt really bad in a foul economy and it might not be a good time to be a route operator, but I don't see the price of pins flooring anytime soon.
What other hobbies are there where you can dump this much money into it and mostly get your money back. If the economy really tanked tomorrow and your pins were not worth as much as an emergency piggy bank, so long as you don't need that piggy bank does that really effect you? If I got stuck with my current lineup... o'well, I guess I'll just have to enjoy this awesome lineup of pins. It also wouldn't effect the value of your collection relative to other pins. You will always be able to trade Spike 2s for other Spike 2s, and a Twilight Zone or Addams can always be traded for a modern Stern. You might also see more "temporary trades".
Even in the case of a real recession, I don't see the price of pins coming down that much. I think a Stern Pro has a floor value of around $5,000 simply because like a tractor, it has inherent economic value and can be used to make money.
Where I do see the potential for real change in the market is on the supply/demand side. If demand for NIB pins falls off a cliff due to pricing and/or lead time to actually get a pin, I see the potential for some of the smaller manufacturers to close their doors. Stern seems pretty safe to me, but some of the smaller operations are, in my opinion, only a flop or two away from insolvency even in a roaring economy.