Have a look around to see what similar plates are advertised for and sell for. If you want it gone quick price it cheaper. I'd have put it in your initial enquiry. Gumtree, eBay or any one of the dealers in plates.
Now here, the problem is no-one knows what you mean by this. Have you tried Facebook marketplace, or eBay, or both? Or is this a general term to mean "the usual selling sites"?
I contacted a registration plate dealer about a plate we had on a company car that we wanted to get rid of, they wouldn't buy it from us but they would sell it on our behalf. If the plate's anything decent that might be worth a go, though it probably would be sensible to get it off the car and onto retention before you do that, so you're not delaying a sale.