The value doesn't drop like that when there's 2 years left, the value drops when there is 1 year left, the point of clubs typically selling with 2 years to go is that it's the last time the club can get maximum value for their player. If its one year to go, they are pretty much at the buying clubs mercy.
Still though, I think as much as this agent tries to hawk Bale around, Levy showed with Modric it doesn't really matter. He will expect another year out of Bale at least.
Still if not, it's a brick load of money to truly shape the squad in AVBs image. If last summer he was playing catch up because of Rafa, Modric and King going, then this summer with a load of money he should be able to get it exactly how he wants it.