Local shop had a fake Nightforce a few years ago. Look really, really good, until you looked through it.
Another local shop bought a lot of "contract over-run" thread adapters for SilencerCo suppressors. I took one look and ruined that poor guy's week. They were butter-soft aluminum and fake.
It is a sad state of affairs, but....
A fair amount of the "airsoft" stuff is higher quality than the low end "shooting accessories" of the same type. Cheap sights, scope mounts, bases, rings, levels, accessory mounts, etc. are a cesspool. But, somehow, a lot of the 'airsoft' market versions are better than the walmart-grade garbage that so many people buy. They are often out of spec in some way, but made with better materials and machining. (Or better injection molding and cleanup, when plastic is suitable.)
In the airsoft world, these things are upgrades and meant to dress up a rifle. They are not the bottom-of-the-barrel garbage meant to make a quick buck at a cheapskate's expense, like the firearms world.
So the airsoft things are at least meant to look good, and are often high quality for the job that they need to do. That is, unfortunately, just enough quality to be better than the walmart-grade firearms garbage.
I was speaking in general, but just realized that I have a perfect example in my possession right now.
I bought my son an airsoft "Sniper" Rem 700-ish rifle for Christmas. It is a "low end" airsoft gun, nothing fancy or spendy.
It has a nicely machined and finished aluminum picatinny rail as a scope base, and is attached well with quality screws into an aluminum cradle inside the plastic receiver shell. Not bad.
Yet, UTG, one of the most popular low end "firearms accessories" (not 'airsoft') suppliers, is making many of their rails now with injection molded plastic.
I'm not saying that you should start buying airsoft accessories. But I am saying that low end is low end. When you buy "cheap", you get what you pay for. And if they're marketed as firearms accessories, they might actually be worse than airsoft 'toys'.