Well it is apparent that it had to be a 3 team trade (I mean the Heat would rather have Toney Douglas than Crawford and Brooks) and then all he could get was a conditional first round pick that will likely be two seconds and a second rounder and had to take on 4 million in salary next year. Some value Crawford has.
The Heat have a full roster, so they wouldn't want to send out one player and get back two, since they would have to cut. (They need a roster spot for all incoming players, even if they plan on immediately cutting any of them.)
Additionally, they got some luxury tax relief, so it would be more correct to say that the Heat would rather have Toney Douglas and luxury tax relief rather than Crawford, Brooks, and having to waive someone else (even if they plan on waiving Brooks and bringing back that other player after he passes waivers).
It's hard to get more than a second round pick for a mid-season rental (the Pacers got Leandro Barbosa for a second and cash in 2012 as an example of typical value), so getting more plus being able to dump MarShon Brooks at the price of Joel Anthony's contract is decent value.