It's not just TG16 getting price spikes this year, PS1 has been insane too. Take Team Buddies for example... was always about $60-$80 CIB and maybe $150-$200 Sealed. Been that way for 5 or 6 years, completely flat. In 3 months, it is now $200-$250 CIB, literally 3x or 4x value in 3 months. And PS1 has generally been dead compared to Nintendo... but the Nintendo overflow has to go somewhere. And some of them are overflowing here, so I don't see TG16 prices cooling off anytime soon. Not necessarily good or bad, just reality.
And I do enjoy playing the games, but I also enjoy collecting them. It is not impossible for someone to enjoy doing both.
Regarding PS1 inflation, I think that the spillover from NES/SNES is getting bad since after SNES, the original PlayStation is considered to be THE RPG machine. It's also got a lot of decent STGs and overall just good variety. The high quality stuff is rising to the top in regards to price when there is not a lot of quantity.
I also (again) blame Facebook groups as they create this fast self-fulfilling prophecy on price inflation. There is one RPG FB group where I feel like discussion of Shadow Tower as some rare gem that's going to go up fast caused the game to jump in price like 50% in a couple of weeks. Forums do the same thing I guess, but people on forums seem to talk less about price speculation, at least that I've seen.