It's the best of the best concept.
NIB games are generally 5500-over 10K now.
Best of the best early 90's DMD games, 5K-8K
Best of the best early 80's games, 5K-8K
Best of the best late 90's oddities and boutique games, 8K-well over 10K.
I don't know what's so surprising. It's been like this for roughly 15 years. If you want the best, you are going to pay roughly the going rate for a NIB machine. Back when an original nice condition Monster bash sold for 4K, a NIB Stern was 4K.