He's a steal for 4.5, but if "we" is the Thunder, they don't/didn't have 4.5 to give him.
And Presti may end up getting the last laugh in the Harden trade. Lamb has some game, but the big steal appears to be Adams. For the Thunder to be able to get a competent Center is a big piece for them. As they start phasing out Perkins minutes, they are that much better. And getting Martin for a one year rental was just a bonus. If RW doesn't get hurt, who knows, maybe they make a run and somehow find a way to make it a series with Heat. (doubt they would have beaten them)
The Thunder need an Adams much more than they need a Scola. They have to get Perkins off the floor.
It's impossible to get fair value for a top 10 player like Harden, but given the situation, Presti may have made off better than people thought and still think.