Yeah, that one you linked has been graded by PSA, and has been graded "gem mint". That's difficult to achieve because in addition to variables that are somewhat within the collector's control (surface condition, edges/corners), there are also those which are completely out of the collector's control, such as centering and printing quality.

383 Stargell cards have been graded by PSA, and only 11 have been declared a 10, which is 2% of all the graded cards. The $750 selling price for this one was a combination of rarity and someone just really wanting a gem mint copy of this card.

Your card's centering is super-off, the edges are fuzzy, the corners are a bit rounded, and there's what appears to be a crease in the lower center. This version of the card is much closer in quality to yours and sold for two bucks.