A Frank Thomas PSA 10 went from $154 to $430

A PSA 10 1990 Leaf Frank Thomas sold for $430 on August 30.
Three months earlier the same card was $154.50.
Card Ladder counted a 178% climb across 29 sales.
The same card in a PSA 9 is still about $40.
It is not rare, 4,749 copies have already graded a 10.

The $40 nine or the $430 ten, which one is actually the buy today?