

I think the market for each is quite a bit different. Prop guns, whether functioning or not, are often regulated in law as “replica firearms” because while they may (or not) be functional, the issue is that they are intentionally similar to the real thing. Hence, some jurisdictions have limits on who can sell replica firearms and who can buy them.
One rank below firearms and replica firearms, air/pellet guns and BB guns propel small balls or shuttlecocks (?) made of metal using compressed air or spring power. These could still be harmful to people, but aren’t usually fatal, which makes them effective for pest control or target practice, in lieu of live firearms. Accordingly, these are often regulated like how knives are: don’t just hand a pellet gun to a child without supervision, and don’t assault people. Otherwise, do as thou whilst.
Meanwhile, airsoft guns propels small plastic balls using springs, compressed air, or electro-pneumatic pressure. By sheer virtue of having less density, a plastic airsoft projectile carries less energy than a BB pellet, and certainly a lot less than a live-fire bullet. Also, whereas firearms can attain supersonic velocities, the speed of sound puts a firm cap on what a plastic, ball-shaped projectile can achieve, when not using chemical-based propulsion (ie gunpowder).
Only 8 US States regulate airsoft guns, and even those that do are not restricting them as heavily as firearms (except New Jersey?). The common requirement is that an airsoft gun should have an orange tip. That means a majority of Americans are potential customers for airsoft, and that means an environment will form that host matches, competitions, and so on. Big market means lots of producers, so lots of variety, high quality, and lower prices for all.
Whereas, what’s the market for replica firearms? Show business? Gun enthusiasts?

Obligatory XKCD: https://xkcd.com/3138/
Please let such a thing never exist!