Even two years ago I found it funny to see that Gunhed was 3 times more expensive than Blazing Lazers. It's usually the other way around with PCE vs TG-16 games, isn't it?
I think Blazing Lazers actually had a larger production run.
I'm not 100% certain, so keep that in mind.
However, I think it is very credible to argue that the reason why Wataru sells for more $$$ is because the production run of Keith Courage was much, much larger (pack-in for TG-16). So, even some early non-pack-in games, especially one of the early HuCards, NEC might have had high expectations on potential sales in North America. Blazing Lazers would make that shortlist (for me, anyway).
This was before NEC realized that TG-16/games were not selling as hoped. Blazing Lazers NOS (new old stock) was shipped off to Europe (PAL TG), I believe. I can't recall if BL NOS was rebadged for Korea (Vistar).
Anyway, the point is NEC was sitting on lots of unsold games.