Hi, I´ve been a long time user (started reading about audio when Nwavguy disappeared), back then people used to recommend headphones like the Koss KSC75, UE4000, Tascam TH02, etc. I´ve had all of those and well today my KSC75s died (the UE4000 and TH02 were taken by my sister abroad) and I was wondering if there´s anything new out there that might be under the 20$ price, otherwise I will buy another pair of KSC75 which are my favorites.
I'm very happy with my Philips SHP9500.
in general rtings.com is a good resource to evaluate them
https://www.rtings.com/headphones/reviews/audio-technica/ath-m50x these are sort of "mid range king" that almost makes obsolete all the more expensive headphones, and if m50x are too expensive you can look at the other models in table, sorting by what you think is most important for you (but I'd recommend first and foremost to look for good THD scores, as everything else can be compensated to some degree) and eventually you'll find something that has an acceptable cost.