I'm only quoting this part as, well.... the people I'm speaking of are from a less niche market than you imagine. I'm not even speaking of people within my social circle and only a select few are collectors. My wife and I are traders, and Trek fans - both long term, newcomers and casual - are some of our biggest customers. The reason being that even at conventions drawing tens of thousands of people, no one is catering to them.
While a con in itself is a niche market (ish), one generic, normal people store local to us (The Works) got in a batch of Star Trek books. Obscure books most retailers are embarrassed to sell as they fit into this niche market you speak of. They were gone in a matter of days.
The stores I was thinking of while posting is asked regularly - not by people making enquiries, but with cash in hand wanting the thing (Beyond Pin). And thats not a guess - I know people workign in the stores.
On the same front, one of the recently requested items in a specialist store (I have a friend who works there) are the new Beyond pins. I'm told there's no interest, but people are going wish cash in hand wanting to buy them. The same store had the same requests several years ago with the 2009 pins. A rival store heard about it and bought them in. They sold very quickly.
I don't want to sound condescending (and sincerely hope I don't - apologies if I do!) - but... there is a market. Trek sells. If it didn't, I'd be in a very bad position right now as thats half our merch! The problem is (or rather, was) the elitist pricing. Forbidden Planet used to stock high end merch - £30 for a Worf figure. No ones buying that. A tenner for a Pop? Sold out. £50 for a Diamond Select ship? Nope! £15 for a Playmates? Sold.
There is a demand - but the few products out there are focused on collectors. That needs to change and that has done more damage than it gets credit for.