I just don't think the Phillies history of spending reticence is applicable here. The more recent history is of Middleton giving Amaro a blank check, even if the other owners and Monty still weren't willing to pay a luxury tax. But Middleton likes to make a splash. He was an animating force behind the Howard and Lee deals (the second one that is), as well as the more modest but still imprudent AJ Burnett signing. And they also gave out the biggest closer contract in history. As Rollins said, he wants to be the Phillies Steinbrenner. And since there are no internal players who will be in need of a big contract for quite some time (unfortunately), and they will be in desperate need of headlines/ticket sales, they will make a run, and they can afford it. The only real question is whether it's worth it to pursue Trout on the trade market as well.
But if they did shy away from handing out a $300 million contract, or from signing an older Clayton Kershaw for seven years, there would be plenty of good reasons for that besides a blanket unwillingness to spend. I think they will spend regardless, just might be four $15 million free agents instead of two $30 million free agents.