I'm reading the text of Caged Sun carefully and comparing it to Gauntlet of Might/Power.
Gauntlet of Might (cost 4)
Red creatures get +1/+1. Whenever a Mountain is tapped for mana, its controller adds R to his or her mana pool (in addition to the mana the land produces).
Gauntlet of Power (cost 5)
As Gauntlet of Power enters the battlefield, choose a color. Creatures of the chosen color get +1/+1. Whenever a basic land is tapped for mana of the chosen color, its controller adds one mana of that color to his or her mana pool (in addition to the mana the land produces).
Caged Sun (cost 6):
As Caged Sun enters the battlefield, choose a color. Creatures you control of the chosen color get +1/+1. Whenever a land's ability adds one or more mana of the chosen color to your mana pool, add one additional mana of that color to your mana pool.
It seems that the Caged Sun's ability prevents my opponents from benefiting, while providing the benefits of either of the Gauntlets. Further, it seems like Caged Sun could be interpreted to work with lands of any sort, including non-basic.
Given the cost of this card is $1-$2 and the other two command moderate to large premiums, is there a drawback to this card that I am overlooking? Surely the 2U difference cannot be the overriding factor here, can it?