The longevity of many is showing clearly in this tread, which creates a very skewed view of the marketplace. Akin to those who purchased an LP in 1970, then an 8 track, then a cassette, then a CD, and down have digital download all of the same original recording.
In terms of trains, many adults with younger kids coming into the hobby don't recall the late 1980's -- because they were not born yet, nor does the fact that MTH released X engine in PS1, then PS2, then PS2 again, and now in PS3 mean anything to them.
On rolling stock paying original 2000 MSRP is akin to a 50% discount off the current catalog from Lionel or MTH, whose prices have risen greatly in the past couple of years. Seeking to pay 50% off the 2000 price on rolling stock, which might have been reissued but is the same molding, trucks, paint, etc., is solely the buyer looking for a bargain without any justification based upon product quality, warranty, etc. It is wishful thinking or pure supply and demand.
I suggest spending a lot more time looking at prices realized at auctions, train shows, and speaking with buyers and sellers, than asking generalized questions here. The members of this forum can all voice their views on pricing, however the market data may well show a very different reality -- one that takes into account the much larger scale of of hobby than is seen here. Lionel and MTH aren't getting by on the couple of dozen "new catalog released" thread relies that say "maybe I'll buy one engine this year," the scope of the marketplace is not the scope of the OGR forum.