What about buy outs? For example:
Trade a guy in the last year of his deal (Ray Allen)
Recieve collection of stuff (V. Carter, J. Boone, #1 Pick)
New Team buys out our guy for $6m less than current deal ($10m)
Celtics resign our guy for full-mle ($6m returned)
Even if it was possible, it would not happen with Ray's deal - the C's would push the $80+ million range, and they are not going there. Pierce's deal, on the other hand...