Why would the Eagles trade Vick? Cutting him this year would have cost them $5M, but if they just wait for the league year to end, they save $10M by cutting him. And they already have $22M in cap space right now. Only $3M of his base salary is guaranteed for next year, plus the remaining balance from the prorated bonus.
The NFL is not a league where you trade players for players. If you're doing things correctly, you're able to cut players that you don't want. You don't swap garbage for garbage like teams do in the NBA (where all of the contracts are guaranteed).
I think they owe Vick $7.2 million in 2013 if they cut him don't they? Sanchez is owed about $1 million more by the Jets. I would think the Jets would just eat the $1 million in base salary then renegotiate a deal with Vick, am I right?