Originally Posted by *BaseClogger*
why isn't "Sol Ring" as valuable as the other nine?
It's not as valuable due to the combination of availability and power level. While the "Power Nine" are all Rares, Sol Ring is an Uncommon; so there are a lot more of them around. Also, Sol Ring was reprinted in the Revised set and the Power Nine were discontinued after Unlimited.
While Sol Ring is a powerful card, it's not nearly as broken as its 0-casting cost completely unfair cousins, the Moxen and Black Lotus. A Revised or Unlimited Sol Ring will likely bring anywhere between $10 to $20 on the open market depending on condition. A Beta Sol Ring can likely end up well over $50.00 even in lightly played condition as it's currently the only black-bordered tourney-legal issue of the card.