How does the NGC Coin Price Guide continue to

How does the NGC Coin Price Guide continue to go down when: the facts: Demand is High, Supply is Low, and the price of materials have went up 12% over the past year. The trend over the past year for Modern Commemorative Silver Dollars have sold 23% over NGC Coin Price Guide value. So where do they get their data. Is a blind monkey just hitting random keys for determining Price Guide value. Here is another fact for you. The 2010 P BOY SCOUTS S$1 MS 70 is valued for 68.75 (as of 06FEB2012). Brand new in the box from the mint (not graded) was about $65.00 in 2007. Now someone is going to say that price guide value doesn't matter.... but it does. Insure value is only what a thrid party (that has no stake in the play) is what it is worth. That would be NGC's Pice guide. I have learned a thing or two in investing an item is only worth what someone will pay for unless you are requesting a claim on a item that you no longer have.