Why is it so expensive to put a stock on a pistol? Is it just about supply and demand or is there something else going on?

I am obsessed with pistol stocks, something about the efficiency and discreetly of them. I bought a brand new stock for my 22 and it was very reasonable. My buddy ordered a gen 5 glock 19X stock about a year ago and its still on backorder. He said they wouldn’t give him a price upfront but his buddy bought the same one back when they released and it was something like 800 dollars and he was expecting this one to be in the three digit range. My buddy ordered 3 gen 5 stocks that I know of and the prices were in the 1200-1500 range. Those prices make me think this isn’t just supply and demand pricing. What else could be a factor in driving the cost up like this? is it because the stl files aren’t available for purchase? Is it because the manufacturers are under pressure to only make so many and help the supply and demand numbers?