They started going up when Spec Racers started buying good Miatas and trashing them/wrecking them/gutting them. Same thing with hardtops. The good Miatas that hadn't been raced became more and more rare, leading to all Miata prices going up.
tldr: all of the above. they are that good, clean cars getting harder to find, content creators ive been driving miatas for 14 years almost. its a combination of age and scarcity of clean cars. and a good part of it is definitely social media, started with the car build channels on youtube, (rightfully) praising how great they are to drive and work on. and its just moved into tik tok as its gained popularity.
