You've all seen the asking prices on eBay, which veer towards the ridiculous. I'm mainly referring to post-1985 Williams / Bally from roughly the "top 50" or so tables. Dealers will be the worst, followed not too far behind by some private sellers. (We might make semi-understandable exceptions for CC, CV, MM, etc. as special cases, or anything with under 3,000 units made.)
The sellers are quick to dismiss valuations like those shown here at Pinside, which I happen to think may not be entirely up-to-date but are not that far off, either. The Pinside values are certainly a lot closer to many of the prices you will see on Craig's List, if you watch it over a decent-sized area for awhile, or to what is seen in the marketplace section here. (eBay does have an advantage in regards to things like Buyer Protection, and often a substantial body of feedback ratings for the sellers.)
Of course, there can be major differences in the condition of a pin (both cosmetic and mechanical), if it was HUO or with a collector, vs. on a route or in an arcade. Still, it is hard to see how this translates into so many concrete examples. I keep seeing various pins that are listed with Pinside valuations of -- say -- $3,500 to maybe $4,500 as the top end figures, where you commonly see them on eBay with asking prices of $6K, $7K, $8K or more -- sometimes a lot more. I'm sorry, but the Pinside-listed values are NOT off by a factor of 2 or 2.5+ !! I don't care if it was HUO, extensively shopped, or what. If you pay that kind of money for most of these pins, two things are very likely to happen. 1) The more knowledgeable folks here are going to say, "What a chump !" & 2) If and when you try to sell them at some future time, you will probably take a bath on it. It will be a prolonged and unpleasant experience, where you won't come close to breaking even on what you spent. And yes, I have been reading the thread on the so-called "resurgence." All I can say is that a lot of people in 2006 / 2007 probably thought that housing prices would keep on appreciating indefinitely too, quite unaware of how close that cliff edge actually was.
I won't tell you that I have not made mistakes like that myself.
[Forget everything I said above, if your disposable income happens to approach that of Mark Cuban's.]
Maybe I should stick to looking for sanely priced EMs. Many have been sitting around for a long time, and the owners just want them gone.