After looking at gems on the AH, I noticed that a Radiant Star was only $1.06 on the RMAH...yet 28 million gold on the GAH.
However, $1 only buys you 4 million gold, whereas 28 million gold is roughly $7.
So...are people just buying Radiant Stars for $1, selling them for 28 mil gold, then selling the gold back for $7?