Welcome to Coin Talk. IMHO the coin shouldn't be graded that high. It has distracting hits on the obverse and reverse. Other members know much more about nickels so wait for their opinions. The reverse also.
It has to be perfect to grade MS68.. Yours nickel has imperfections. So do all the other trillions of coins in circulation.
I don't see a stated condition for the coins, which may have been selected from circulated change, normally worth face value, placed in a custom holder. It would be difficult to place a "market value" on the set, but I wouldn't imagine any where near $625. I believe they're worth whatever a buyer will pay, and you may have established their value by your purchase. I have purchased proof-like coins/medals from a mint, in custom holders, which I haven't been able to sell, given as presents to entice others into investigating collecting. JMHO
Welcome aboard! It would have to be certified and in their holder to be arguably worth that kind of money. Unfortunately, the coin you show is nowhere close to a 68.
PCGS prices are as good as the Red Books prices. They are just a guide. The nickel you show has way too many marks to grade a 68.
If you bought a roll of uncirculated 2004 d Nickels chances are you would get several that were nicer than the one pictured.
