Posted By:
Eric BrehmI subscribe to VintageCardPrices.com and have found it to be very helpful in assessing market values; it will become more so in the future as their data base of historical prices grows. SMR meanwhile can't react to every minor fluctuation in the market; they could for example raise the values on T206's because of recent sales activity, only to find them come back down to earth again.
SMR is good for assessing value changes over the long term, and as I said before, as a baseline for the relative values of cards within a set. On some scarce high demand items (either truly scarce or condition scarce) buyers completely throw out the book when bidding, but otherwise I think most do use it as a reference point. It is to a large degree self-fulfilling prophecy and PSA wields considerable power to influence the market with that thing.