Similar to coin craze years back, when an NGC MS70 would sell for 20 times what an NGC MS 69 would sell for, yet they were IDENTICAL coins. The trade was about the holder.
This book is a $40 to $50 book. It is being dressed by plastic with a grading label on it, but it is a common book, with no unusual printing defect flaws in run, no great warehouse fire story to eliminate 95% of the population. Virtually any and every comic collector, like the 12 year old who spends his paper route money on it, have a copy of this book in as issued condition. It is a ultra common.
But so what, if someone wanted the best graded example right now, then there is a premium, to land the only 9.9 Maybe this purchase price represents 1 hour of the buyers time. Maybe he would have gambled it away at the blackjack or craps table (as many people do all the time) but chose to spend money more wisely than that and have something to show for it. Buyer seems thrilled with purchase, price is reasonable as of today.