And they are "easy" to build yourself. I wrote a guide about doing so here [0] which is based on this enormous head-fi thread [1].
0: https://github.com/Azrael3000/headphone-guide 1: https://www.head-fi.org/threads/my-diy-electrostatic-headpho...
0: https://github.com/Azrael3000/headphone-guide 1: https://www.head-fi.org/threads/my-diy-electrostatic-headpho...
For those who are interested in entry-level, non-DIY route
Drop (formerly Massdrop) has their variant of the classic Koss ESP/950 electrostatic headphones for around $500. They sold out earlier this year.
https://drop.com/buy/massdrop-x-koss-esp-95x-electrostatic-s...