As a teen I managed to 'rescue' 1000's of £/$'s worth of graphics cards from eBay listed as spares/repair with this method. I recall this working about half the time; then again at least 3/10 cards from eBay listed as broken worked immediately when plugged in.
Did you have any "signals" you looked for on the listings to indicate they might just need an oven reflow, or did you just buy everything cheap and hope it worked?
