i own a jdm and if i had an extra 20k lying around itd be worth it (its in the shop rn racking about 1500 in repairs -_-). I think the hype comes from the endless list of mods that are available for these cars from purely cosmetic to performance parts. If you have enough money these cars are essentially Theseus' ships. Another reason I can think of is Japan's modding culture in general, from Bosozoku cars and bikes to simple, undertone-esque mods. I don't know how to word it properly, but if I'm ever looking at a car that's for sale in Japan, they almost always replace the rims or something similar. I mean, in the US it's pretty similar. Media also hypes these cars up; Fast and Furious, Initial D, racing games, etc. From a more technical side some of the engines are very impressive; Honda's DOHC engine, Toyota's 2JZ, (Mazda's rotary engine can be decent if you work out the kinks), and even Nissan's VQ engine (had to mention since i have one) are all solid, long lasting engines. I think their affordability and unique sporty looks are what make high schoolers flock to em and clap the mess out of em.