I like to look at sold eBay auctions as a starting point for pricing books, especially those I don't follow regularly.
I don't see a photo of the inner flap of the DJ so I'll take your word that you know what you've got.
There was a listing at $795 in November (or best offer) and the seller accepted a best offer. In my experience that's within 10-15% of the asking price.
https://www.ebay.com/itm/275552035361?h ... 7675.l2557
You can compare it to your book and get a range from there.
I have to say I'm surprised that it sold for that much, but I haven't been tracking later King printings.