if you check here Morgan Dollars (1878-1921) | Price Guide & Values | NGC (ngccoin.com) that $625 price is for a MS63 of that year unless you are asking "why are Morgans of that year and mintmark valued so high?"
I do not know how you searched but this is what I got on searching for that Certification # and Grade (Other/Circulated) ... as below you see "NGC Price Guide Value Not Available" maybe there's a bug in the app version (I used the web version https://www.ngccoin.com/certlookup )
I choked and spit out my coffee when I saw the signature on the slab. The ONE and ONLY coin shop in Helena, and in fact, for over a hundred miles from Helena, is Wayne Miller. I've only had limited dealings with him, as his store reminds me of a hoarders lair. Coins and albums stacked all over the place, with seemingly no order, but I'm sure they know where things are. I found out that Wayne is considered an authority on Morgan and Peace dollars, which I did not know. From https://www.greysheet.com/news/story?title=wayne-miller-the-king-of-silver-dollars "numismatist Mark Salzberg, whose third-party grading service company, Numismatic Guaranty Corporation (NGC), is paying tribute to Miller with a special certification label hand-signed by the legendary researcher, author and dealer." Interesting info, especially if you collect Morgan and/or Peace dollars. Thank you for this post.
