Posted By:
runscottDan,
here are two cards given the save grade by SGC, the one on the left for rounded corners and stains, though no creases. The one on the right is a near-perfect card, but has the slightest surface wrinkle on the back, that is nearly impossible to see now that it's behind plastic; however, ANY wrinkle, no matter how small, prohibits a card from grading 'EX'.
As the other Scott pointed out, you should be buying the card rather than the assigned grade.