I dont have a store nearby, so i do most of my headphone exploring by buying and reselling used headphones. Havent made a profit nor a loss in 20 or so headphones. But in my country (Netherlands) the market is pretty bad, especially with the higher end stuff. People try to sell their (ab)used stuff often for more than new price and get annoyed when you offer them a more realistic price.
In PH the second hand market is great. They frown upon “flipping” or basically selling your item for more than what you got it for, basically kills buying and selling of such iems/hps. You get kicked out of audio groups if you get caught flipping. I do appreciate this actually since you want to be inclusive of people in the hobby
Part of the reason why I was able to get a vxv, noble k10, shure se846 for a combined price of 600usd