The Red Sox did buy at the deadline. The Red Sox did not go all in and move any of their top ten prospects to improve the current roster. They went shopping, but with a budget.
Whether they should have done more is a matter of opinion, but they clearly decided to operate within a limit. Craig Breslow put it like this:
Breslow: "My guess is we traded a lot of major league talent today. But this is where we are and I think the team has shown they deserve to be reinforced.