Lets not forget the return we got for Rondo. Mind u he never had his said he was leaving. With that said, a late 1st and either an expiring (Thornton, Prince, or Bass) or Bradley should get it done. We also have the TPE, although is rather keep it for someone else
A key factor is that Dragic is cheaper, which means more teams can match his salary. The more potential buyers, the greater the price. It only takes $5 million in outgoing salary to trade for Dragic if you're below the tax, and $5.9 million if you're above it. Compare this to the $8.6 million and $10.2 million, respectively, it took in matching salaries to acquire Rondo. Furthermore, Dragic's cap hold next season is less than the salary he will be seeking (and likely get). So if you trade for him now, and you're a team that would have been able to sign him with cap room, you've created cap space. Specifically, Dragic will probably get $18 million next year (don't laugh. He will). His cap hold is only $11.25 million, however. So if the Celtics were to sign Dragic as a free agent, they'd need $18 million in space. However, if they trade for Dragic, and agree to re-sign him, they can count him as $11.25 million against the cap while they use up the remainder, and then sign him to his deal with Bird rights, essentially creating about $7 million in cap space. On the other side, Rondo took up the entire max salary with his hold. Finances have a huge impact on trades, and accordingly, I would expect Dragic to be more valuable on the trade market.