Well, the seller from whom I got the IN-16's claims that people use them for clocks or re-gas them. For the latter you'd better look for an Alchimist and I don't think re-gasing small tubes makes sense as of 2020 (yet). As for building clocks with duff nixies, I realised that it is not about building "nixie clocks" but probably "clocks with nixie parts", like sticking their digits on the dial face! Given the small lot I've got I might begin using these digits to add a timestamp on my clocks :) Other uses would be as former USSR souvenirs, novelty items to visitors, ... at 50c a piece for IN-14 makes almost sense.
Deviating from the subject of the thread, few of those IN-16's happily react to HVAC with lavender/violet discharge. So, either Neon has outgassed leaving Argon alone (heavier atomic mass), or those tubes were never inflated with Neon (production error/end). The question is ... how much DC voltage should I need to light it up as a Nixie? 300V were not enough.
Paolo