Even if the deal was the 2017 Brooklyn 1st + the expiring contracts of Zeller and Jerebko, I don't think I'd be that thrilled about moving for Butler. And everyone says it would cost significantly more than that.
If you land Butler for a deal that includes Bradley or Crowder and our key picks, you're basically going all-in on a 5 year window around 27 year old Butler, 27 year old Thomas and 30 year old Horford. And that'd be fine, except there's a team out there that has 4 All-NBA players (two of which are MVP level) all in the 26-28 age range... and I just don't think any one player outside of LeBron James, even without loss of key players, is going to make us a real contender with that.
Also, personally as a fan there's nothing more fun to me than watching a young guy develop into a star. Watching Pierce develop into the player he became was so much fun. We got to see that early development with Big Al, but he got moved and never reached his full potential. it was a lot of fun watching Rondo bloom as well. This 2017 draft is said to be epic. Even if the pick falls in the 5-8 range, we're looking at someone who should be a better prospect than all the options we had available at #3 this Summer. I want to see these kids grow. I want to see the next Celtic great be home-grown... not some mid-peak castoff from a Bulls team that already deemed their star player not good enough to build around.
if what they say about this 2017 draft is true, this is a special one. You don't often get a crack at a top 3 pick in a special draft. This is how franchise players come into the world. I'd rather gamble with that than gamble on some top 20-30 player moving the needle enough to compete with the Cavs and Warriors in this 5 year window.