Well, it's not even bought for 3000 gold. "Gandalf the White" is a spell, so you get it for 3 spell-points -which actually makes it a really strong spell, because those 3 points amplify 3000 solid gold. It's actually like that: The strength of "Gandalf the White"-power has absolutely nothing to do with Gandalf's 3000 gold, it only has to be viable for its 3 spell-points. If Gandalf in general isn't worth 3000 gold, that's a totally different thing, but buffing the hell out of a poor second tier spell is most certainly not wise.
Greetings
Melkor Bauglir