I just received my Koss ESP-950 headphones from drop. These are some of the most affordable, comfortable electrostatic headphones now made. Electrostatics yield - imho - a much finer treble response than diaphragm based phones. The midrange is to die for, though doesn't quite compare to my STAX 009s, at ~ $4500. list. At this price, $400., (list is $1000.) it is an insane deal. https://drop.com/buy/massdrop-x-koss-esp-95x-electrostatic-system Note that the pads have been redone by massdrop (foam and velour, making comfort even higher), and there is no battery pack, just an "energizer" with a wall wart (and no leather carrying bag)
In Europe, it is or was even cheaper (~$250. US), but I can't properly access the UK site, because it is blocked from the US. It was about $250., as drop, formerly massdrop, tries out a new shipping system. At that price, they will or did sell out.
Why is it most professional musicians have horrible audio equipment?