Strasburg for Betts (and let's say Betts and stuff), with two years of control on Strasburg makes sense. That doesn't mean it is a go but that is the sort of deal you trade premium prospects for. I don't think the front office has any absolutes with guys on the touch/don't touch. (or more accurately I don't think Cherington does, but his superiors might) Hamels a little less so - he has more control but less peak too. The Red Sox do have the ability to take on money - and there is some value to that in and of itself.
As UN pointed out, cases have to be made individually. Price was sold for a handful of magic beans - and you can only surmise that there was downward pressure to deal him. Considering Friedman and Maddon's departures, it would not be a surprise that ownership had a lot of say in the move. With Lester, the return was fairly good - 2 years of starting level outfielder for 2 months of Lester when you consider the Price return. Also, with the new rules around compensation of traded guys, it suddenly made renting Lester easier (since reacquiring does not have a pick cost).
I think you have to consider Betts, Pedroia and Bogaerts as your every day guys and the other 5 positions are very much negotiable. Napoli and Cespedes are the most attractive guys to deal off the major league squad if you are trying to put together a deal for something you need. (aside from the kiddos)