You bring up some very valid points and I look foreward to more posts on this subject.I know it is hard to come up with prices for a guide because I am sure there is not much to go on.Auction sales is one way but who could monitor all those.It is not like the coin industry where there are many retail outlets to pull prices from or the wholesale trading which would establish a low range.It is the best guess of the price guide authors who also go by contributors from around the country.
I often wonder why a 3rd edition scarce card is listed at 3.00 and the 8th edition card from the same casino is listed at 3.00 when it is impossible to find the 3rd edition anywhere in the casino at any time of day or night.
The whole key to increasing prices as it is for other collectibles is to get more people interested in collecting cards.