You can take in salary up to the TE -- thing of it as a placeholder for a real contract that's worth, say, $10 million. Or a salary gift-card, if that makes it easier.
We can't just take Asik from the Rockets for draft rights because we'd be over the Luxury Tax, but if we sent, say, Jeff Green to the 76ers for Elliot Williams (not that we would, of course, that's just an example), we'd have enough room to just "trade" Asik for our Exception -- which would then create one for Houston based on the 8.3 million difference in salary they sent out.