Still waiting for that planar magnetic with open back and FR like sony wh1000xm5.

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

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.

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).