Their form factor is perfect
Yes I agree it is amazingly light, I believe lighter than most all other portables, even the Sony I mention below.
The wood is nice but honestly it makes you wonder why the MSRP is 600-700$
Yes I understand, but you can do much worse in spending department, with an expensive top Ultrasone model, which to me is not at this level. You can find these used and usually very well kept. I got mine as an open box for less. It really is the headphones wood and driver that most value is in.
It has a very good driver that reaches higher than most its size. Unfortunately the signature is viewed as "W" or not natural, which is where the recent suggestions of the pads make a huge difference.
I believe it stays in a nitch as a nitch product.
Even for an all plastic build my wife's Sony MDR-1AM2 feels better built and it's much cheaper
This is actually the only other portable I stayed with due to rugged portability with an over ear. They are also the only portable Sony which employ the stiff membrane in their drivers, which only their top models have (stiff membrane).
Unfortunately they only hint at better performance, and signature-wise can be a bit dark, while the WP900 is operating at a higher resolve and are lively.
Although the WP900 is still a bit below a Denon9200 in resolve, that's OK as no other portable closed headphones (except Focal) reaches higher than the Denon9200, unless you go with a top planar (like an LCD5), but hard to find any good closed back.
I don't mention anything else which are to me mid-tier, because many get duped buying expensive & beautiful wood full size closed headphones, or portable earshaped planars which I tried and they all weren't actually any better, just another choice.