First off, the Jays' package was Lawrie, Graveman, Sean Nolin, and Franklin Barreto. The Jays did not want to give up that much for Donaldson, but Beane insisted. It looks like the Jays still got the better of the deal, but I would not go so far as to say that Beane was fleeced.
Secondly, the timing of events is not known. Supposedly, Anthoupolos had called Beane earlier and asked about the availability of Donaldson, and Beane said no way. It was only about 2-3 days before the trade actually occurred that AA called Beane again and the talks got serious. After the Sox already signed Sandoval.
If Beane had planned to trade Donaldson all along, do you really think that Ben would be unaware of his availability? Beane, knowing that the Sox were in need of a 3rd baseman, surely would have contacted the Sox if Ben had not already contacted Beane.