Three years ago I really wanted a SM. Took ages to track one down and then a couple came up in the 2.8-3k range, Last few I've seen have been in really good condition but seem to have gone for 2.5, maybe a bit more. Didn't have mine here for a year or so and when I got it back the flipper action felt strange compared to newer Sterns.
I paid £2.2k for my LOTR but that was about 6 years ago. At the time I could have got a better one if I'd hung on a while. They seemed to then climb to around 3k but I thought they'd fallen back a bit again. Probably the key issue is that they don't crop up often. The only LE I've ever seen was one from PH which I think had been damaged in transit on the bottom. IIRC I think Phil wanted less than 3k.
MET pros have dropped and seem easy (ish) to source. Haven't seen a premium for sale though so suspect they are still at a high price.
AC/DC has come down slightly in value for the premium. although the PRO is rare I would imagine it's totally tanked in value. Who the **** wants that fugly thing?
Lots of other modern sterns have settle din the 2-2.5k range that the better B/W games are also in.
SEGA's are all over the place. I still think most are sub 1k but I know I've just made way more than that for a Godzilla. LIS is probably the hardest to source but went for less than £900 on ebay this year.
DEs what the **** is going on? The runt of the litter has just become sort after.

Last year a LW3 went for more than a grand. WTF. What next LAH for the same amount?
Back to the LOTR question. If I was Gary Stern and had an efficient well run factory that has a history of being able to crank out machines (as well as a brand new factory) I would have stockpiled the bits I need to build a vault edition LOTR over the last 12 months. I'd now be waiting for another badly run competitor to finally get their **** together and announce a firm release date for their very delayed very similar themed machine and then drop my game on the public in the same month. No waiting time for actually be able to buy it, no 1000 people in front of the new customers who's machines need to be made first. Hey presto a small dent in my sales of a Vault edition (which is near enough all profit and has the stronger theme of the two) but a loss of 300 or so badly needed new sales of the other machine and then no more future competition. Maybe Mr Stern isn't as nasty as me though or maybe there are licence issues to prevent this but I really wouldn't be surprised to see a VE crop up later this year.