If anything is degraded, it is the earpads, however it is unlikely they are. Even so, replacement earpads for the PX100 aren't so expensive. i say go for it, as long as you are reasonably sure it is real and the seller is legitimate. A number of years ago I bought some old model Sennheiser compact headphones, and the earpads were crumbling.
Some people greatly prefer the single side cord on the PX100II to the dual entry PX100. $41 is a good price for the PX100II. It seems like US dealers are asking around $70 for it now. My PX100 is a few years old. I paid $40 for it. I would not pay $70 for the PX100II. For around that price, one could get a Sony MDR-V6 or a Koss Tony Bennett headphone. Those are much more substantial. Imo the PX100 is only slightly better than the $15 JVC HA-S160 "Flats". While the Flats is closed and the PX100 is open, since the Flats is so small, it doesn't isolate well. I prefer the sound of the $40 JVC HA-S650 to the PX100. Both are warm sounding and have plenty of bass, but the HA-S650 is closed and has more bass punch.