Yeah. Your 200$ pricepoint is fine, OP, but knowing the seller in question is a big variable. When you're searching classifieds, reputation of the seller is everything. I may pay more from someone that I trust, but I still wouldn't pay anywhere near new - Anyone suggesting that a near 300$ price is the norm for a used 7970, well, good luck with that. I have seen among many classified forums (OCN, here, HardOCP) 780s and Titans with substantial discounts. Keep in mind that a used card doesn't have software bundles, the warranty is partially used and may not be transferable, may not include all accessories, and a used card may have been subject to prior owner abuse. You simply do not know what the prior may have done to the card, and for this reason - unless a card is BNIB a used card will always have a substantial discount. Anyone selling for a near new price will probably have difficulty finding a buyer.
Long story short, I personally think your 200$ pricepoint is okay depending on how much you trust the seller. 225$ at the high end for used. But not more than that IMHO.