Some people just want savings, however slight. Also, some vintage pieces come in stones or configurations that are no longer available new.I did some searching and noticed Hermes resell is 50-60% of its retail price. It does not seem to hold its value much like most have mentioned. This tells me that buyers don’t value Hermes jewelry as much. However, VCA even when used, sells close to retail price. Why wouldn’t people just buy new VCA since resale prices are so close to retail prices?
Don’t forget that what you see as the resale price is not what the seller realized, unless the seller sold directly to the customer. The middle man in resale always takes a hefty chunk. So if for example you see a Hermès piece selling for 50% of new, the seller only received 25-30% from the middle man.
Hope this helps a bit.