EBay was fun two decades ago, when I bought a nice Stellarvue Apo telescope as well as some used audio gear for a second system.
I find it to be a mixed bag now, sometimes a cesspool. With the exception of some brick and mortar stores using it as an outlet, audio gear is typically exorbitantly priced and often shady. Want to pay double for tired C-J gear than on Audiomart or Audiogon? I’ve been cheated, for example, from a fake New Balance outlet store that gave an explanation for why my shoes were months late by saying “they were on the boat from China” for US-made shoes. I was reimbursed for this fraud from my credit card. But I used to order New Balance 990’s from a legitimate NB outlet on E-Bay, not anymore. There is no longer oversight of the shady stuff it seems.