Most comfortable headphones

I want to give a friend a pair of headphones that not only "sound" great, but that are also very comfortable. Any recommendations. Up to $500.00.
I own and would highly recommend the Hifiman HE400S you can get on Amazon (Gramophone - same place I bought mine) for $249. They are very comfortable over long listening sessions and are pretty lightweight (especially for planar ‘phones) that also aids in comfort.  Their sound is neutral with excellent detail but avoids sounding harsh, and they can even be driven by a phone but will scale up with a better amp/DAC if you ever want to upgrade.  The main downsides are they are an open-back design that gives them an expansive soundstage, but sound does leak out of them if that’s a consideration.  Also, they are a little funky looking due to the headband, but that’s also what gives them some of their comfort factor.  Other than those caveats I’d highly recommend them for comfort, low power requirements, and sound that punches well above their price point.  Hope this helps, and best of luck. 
My partner stays up all night listening to the tv and music using Sennheiser 600’s. She has had the same pair for 20 years... we have an extra pair in case these wear out. She frequently ends up sleeping with them on. Kind of the definition of comfortable. The new 660s have the same form, although sonically have been upgraded are $499. Sound is outstanding.
Sennheiser 6xx. I have a dozen headphones, these are the most comfortable by far and sound great. 
Grado, they range from $80 on up. Light weight. They are all open back so not good for noisy places, just FYI. 
I have found that the Brainwavs leather upgrade pads really increase the comfort of headphones. (totally better than most stock pads).

Other than that, some headphones have a tighter clamp spring which some people complain about.
It depends on what kind of headphones he likes. If Bluetooth, you can look at Sony I have had them for 6 years, and I do not want to change. Along with them, I used wired headphones for the computer, but the wires are constantly getting tangled. And Bluetooth doesn't break as often.
It depends on your friend's requirements for headphones. If he likes headphones, he could choose Sony and Beats. If your friend likes bone conduction headphones, he could choose Naenka and AfterShokz.

For that money, Audio Technica makes some mean Bluetooth headphones. If your friend doesn’t have/doesn’t want an amp/cd player/DAC etc. and listens to music with a smartphone/laptop, then Bluetooth would be the best option.

Another option could be the Sony WH-1000XM4 noise-cancelling headphones. They sound very good and balanced; unlike many of the celebrity headphones lurking out there.

How comfortable a headphone wears is a personal thing. Over-ear headphones would be more comfortable than on or in-ear monitors.