Discover do have a "sell" facility.
Sending individual LPs in the post sounds like a miserable business though.

If the money is important discogs does at least let you see quite quickly how much something has sold for in the past.
Bear in mind the higher price might be for something in mint condition.

Here is an example
https://www.discogs.com/Fairport-Convention-The-History-Of-Fairport-Convention/release/1682768
Type something in the search box to see how little\much your records might be worth.