Resume Robert is obviously not a record collector.
Prices for records are determined by many variables, not just rarity. Errors, notoriety, death of the artist, etc., etc
Records that have been reissued on cd still fetch large sums on a regular basis. True record collectors/music collectors realize that analog vinyl is sonically superior to digital compact discs and is a more accurate representation of how the music sounded live in the studio.
Still sealed records (to collectors, abbreviated as s/s) ALWAYS fetch a premium over an opened copy.
What you have is rare because it is s/s. Cash items have been consistently in demand since his death. I auctioned a modern non-tour t-shirt three years ago with what I thought was a steep "buy it now" price. By the time I finished listing and checked to see how thye item looked to buyers it had sold.
So...what is it worth. At least $20.00. Possibly much more, especially in an auction if you get two or more people bidding against each other.
Antiques and Collectibles are worth what someone else is willing to pay for them at the time you are willing to sell them.
P.S. Out of curiosity I clicked on "resumecrazy's" link. It is an ongoing auction that still has almost two days left. A search of COMPLETED auctions showed ten recent sales at over $20.00 each. One was 29 dollars and change, another was 26 something. Both were OPEN copies. I would assume yours would go for at least 25% more.