If they had just waited one more year they could have looked at things a bit more clearly, IMO. He'd have been one year older and coming off a lesser season ("only" 31 home runs after four straight years of 45+, fewer RBIs, 70 points lower OPS) and the team's disappointing playoffs. But the main thing, as noted, was the cost. To get the deal he did when he did for as long as he did it should have been cheaper. Or else, yes, shorter.
All of Amaro's moves to not bring back a player, OTOH, backfired. Ibanez was okay but he didn't really make the team better compared to Burrell's more OBP-minded approach (and it was Burrell who got another ring once he got back to the NL). Werth was never properly replaced. Trading Lee led to Oswalt and then getting Lee back. Even cutting the cord on Victorino backfired IMO though at that point they had luxury tax issues (but, they should have thought of that before they signed all those other contracts).