Avantone Pro has launched the Planar II, a revision to its reference-grade planar magnetic wired headphones. It features an open-back design ideal for hi-fi listening and professional mixing use, and is now lighter for enhanced comfort over longer listening sessions. The Planar II is now available for US$399.https://www.notebookcheck.net/New-Avantone-planar-magnetic-headphones-deliver-audiophile-sound-at-modest-price.755075.0.html
The Fostex T20RP, T40RP, and T50RP are planars under $200. They've been around for decades, though with some tweaks (the current version of the T50RP is the third generation, or MK III).
It's hilariously wrong to suggest that these can be easily driven by a phone or computer because of their low impedance. All planars are lower impedance, typically no higher than 48ohms - but they're very sensitive and require a lot of current. You'll 100% NEED an amplifier that can deliver a lot of power into a low output impedance - probably at least 2.4W into 32ohms.
$399 is not a modest price for planars. That's pretty typical for a mid-tier planar. You can get pretty decent planars for as low $109 for Hifiman HE-400SE.
Planar magnetic headphones are not unique nor do they usually cost over 1000$. I use hifiman Deva pro. Planar magnetic headphones with a seperate (included) bluetooth receiver clicked on. They cost $350 and are the ideal multi use headphones for me. I do use them at least 5 hours every day.
The non pro Deva is even cheaper
Still waiting for that planar magnetic with open back and FR like sony wh1000xm5.