To be perfectly honest, since Soul Wars has been released, I've seen a good fifty 10 HP Obby Pures.
They're really nothing special, other than to be level 30 and have 85 STR.
I mean, PK wise, they're rather trash.
The max wouldn't be enough to 1 hit KO someone, and you have to assume a level 42 could easily hit a 10.
I'd say no more than 30$, give or take.
*Edit*: Note sure what the max would be, just assuming.
Even if your max is plenty enough for a KO, you've gotta survive 10 seconds if you fail. lol