Look at it this way.. You put Vanek on the market at 75% of his cap. You retain 25%. That's only 1.775 million you are paying for one year. Mind you, in a year you'll have cheap forwards and can afford it cap wise.
You trade him (indirectly) for support guys, veteran guys. You could probably get 2 or 3 of them at Vanek's cap space. I'm talking Ryan Clowe's and Mark Streit's. Now you've still got some 1st and 2nd round picks from the Vanek trade to use.