With so many items already out there and new pieces being produced year round by all the major manufacturers, it is becoming interesting to see what pieces are considered rare or scarce and in high demand these days. There are certainly many 'rare' items but most are not necessarily 'in demand'. I happened to watch an auction a few weeks ago (just curious you understand) of some K-Line aluminum cars including the beautiful NP 21" set. The 4 car set went for $600 which is certainly reasonable while the 2 car add-on RPO and diner (I think) fetched well over $600 for the pair.
Today the 21" blunt-end Domed UP observation car brought $610 (with only $9 for shipping) by itself. These don't turn up very often do they?
What are your choices for rare and in demand?