Yes, it's just basic supply and demand economics at play. If/when FRTs ever go away or the market is saturated the price will drop to 'normal'.
The reason they can sell them at the high prices is that FRTs have upped the demand so much. No doubt nearly every day someone that has one lets their friend shoot it and before the end of the day the friend is online looking for a TX22, FRT, and magazines.
Right about a year ago I got mine for $250 and it came with a bunch of extra magazines. Then in September I got the TORO model for the same price but with just two mags. Soon after that you could hardly find them.
A couple of years ago a friend got a Gen 1 TX22 and he was jealous because at the same time I got a SIG P322 and he liked mine better. Now I'm jealous of him because his heavy slide Gen 1 runs with a suppressor just fine with no extra parts or playing around.
You never know what will come out next in the gun world. Interesting times.