This may seem like a no brainer, but since I've kinda leaned towards the more inexpensive tinplate train market rather than the more often very expensive scale market recently, I've noticed that some of the newer tinplate rolled out by MTH has become a bit harder to acquire.
For example, I recently sold my prized Lionel Classics Blue Comet set in favor of a version with Proto 2 or 3 (yes, it was tough to say goodbye to it). The funny thing is when I sold it on the bay, it sold for much more than I thought it would (Almost $150 more specifically). In the same turnabout, actually finding a new Proto 2 or 3 Blue Comet set is proving to be a challenging hunt during this Thanksgiving season.
It may be just the popularity of this set in particular, but to me, it seems tinplate trains get more popular during the busiest, most jolly time of the year. Which makes sense overall, since tinplate really fits in the overall Christmas mood.