Sales transactions for graded cards sold on eBay and major auction houses can be found here: http://www.vintagecardprices.com/basketball-card-price-guide.htmGo to the top 25 chart for cards sold in...
eBay is a good place to see what collectors are currently paying for a card, and this is what the value of a card is based on. Do a completed items search on eBay for the card you are looking for....