For a limited run, 400 units is higher than I would expect for long-term value. Lew Horton often specified 300 units maximum for their limited S&W offerings. Quite often, the numbers were less than half of that. Some of those took years to sell.
I also do not accept statements that there are more than 600 people ready to drop $7k on a pistol inspired by a movie at face value. While there are very well-heeled collectors, the pool of people willing and able to drop $7k on a pistol is fairly small, and not all of those people would be moved to open their checkbooks for this pistol. I may be wrong, but the cynic in me thinks the "sold out" message is a way to use the "fear of missing out" to sell more pistols.
[ETA] I pulled the BATFE manufacturer report. In 2020, Les Baer made less than 1000 pistols. Infinity made 554 pistols. STI made just under 16000 pistols. Les Baer made less than I expected while STI made more. Caspian and Foster together built less than 1000 frames. Wilson made just under 9500 pistols. TTI did make 21 rifles. [/ETA]