That's some pretty profound wrinkling.
This kind of issue should definitely have been mentioned in the ebay listing. Trying to slip something that serious past a unsuspecting consumer is just wrong. I assume that you did your research...feed back, previous sales of camera equipment (not Hummel Figurines), and whether or not the seller accepts returns (that's the big one).
It should definitely go back providing you have that option. After, and only after, you get your refund you might want to post some negative feedback, but that depends on how graciously the return is handled. Maybe, just maybe, he simply missed it...yeah I do tend to be a Pollyanna.
It's a bummer to receive something like that, but there are plenty of nice ones out there, so don't give up on the Pentax 6x7, it's a great camera with an astounding array of lenses available.
Best of luck on the next one,
JD