Kind of depends upon what it is, and the era. Some items are still fairly common and easy to find. Condition is also a large factor.
In researching the listing of a AHM/Lima 2-6-4 (I'd call it a 2-6-4T) I found it has the flat/pancake motor and a grade of C from Spookshow, if it runs. It is listed as $99.99 plus shipping, no mention of running condition and no returns. The side view looks like some of the valve gear is missing. Were some production lots made with simplified valve gear?
Unless you're collecting it to sit on a shelf, don't bother even if it's absolutely pristine. There's a reason you don't see locomotives with pancake motors anymore- they're terrible. I can't think of a single example of a good application for the things. Pancake motors are one of the worst ideas in model railroading history... they're cheaply built and perform about as well as a twisted up rubber band. Never, ever buy anything with a pancake motor.
When will HSM products run out. It said to see people think these are real N scale trains. http://www.ebay.com/itm/MIB-Souther...019899?hash=item2cb028b93b:g:xZoAAOSwaB5Xl6E5
567 pieces of Minitrix snap track http://www.ebay.com/itm/MINITRIX-ON...076816?hash=item2caf357390:g:88gAAOSwgApXATKt
87 MT cars...a vague listing (involving only the type of car) and a few bad photos, and he wants almost $16 a car (can you say 'pig in a poke'?) AND $50 shipping: http://www.ebay.com/itm/Micro-N-Sca...138189?hash=item33bc2909cd:g:ZisAAOSw0fhXl9IM
A lot of 10 Atlas engines...shouldn't it cost less when you buy 10 at a time? $150 ea: http://www.ebay.com/itm/RARE-Collec...199950?hash=item1a18060f0e:g:KiIAAOSwcdBWRnQW
Home office kit? What's this doing in N scale/Parts/Buildings, Tunnels, and Bridges? http://www.ebay.com/itm/Nexera-4006...502712?hash=item58df1f74b8:g:Qy8AAOSwanRXhfr5 http://www.ebay.com/itm/Nexera-4004...502754?hash=item58df1f74e2:g:3sQAAOSwRgJXhfr-
How about a Tomix roundhouse? I could almost build a full size one for the price: http://www.ebay.com/itm/TOMIX-Struc...893661?hash=item1eafa5bd9d:g:ZrYAAOSwaG9XIpx2
Why...just why?!! B&O 4449 warbaby with DCC and sound...why? http://www.ebay.com/itm/N-KATO-DCC-...312720?hash=item46508fcf50:g:QBUAAOSwRQlXcvGF
A table full of crap: http://www.ebay.com/itm/TRAINS-HO-N...778046?hash=item281ccb4f7e:g:tHkAAOSwiO9XiT3l
Answer- When they're all in a land fill somewhere. It would require a massive public information campaign, to teach everyone what they do not actually possess.
I guess we are supposed to spend hours trying to figure out what pieces those catalog numbers reference.
Gotta love international shipping rates, : http://www.ebay.com/itm/Athearn-Mil...482972?hash=item4b05d6619c:g:cmgAAOSwaB5XqCDD