They sign LeBron to a max extension, $20 something mil for what, 6 years? They also make the Mavs take back Antawn Jamison ($28 million the next two years). That's $33 million in 2010 cap space they send to Dallas. Dallas sends back Dampier/Butler/Stevenson/Roddy/Najera (that should work under the cap). Cleveland sends out $33 million in committed salary for 2010, they bring back $20 million in committed salary for the upcoming season.
In addition, after 2010, Butler/Stevenson/Barea is off their books. They'd be going into the summer of 2011 with $40 million committed to the 2011/12 season, a starting guard in Roddy, a lottery pick, Dallas' pick. If LeBron leaves, 2010/11 is going to be a lost season for the Cavs no matter what, but it would quickly set them up to rebuild quickly. If they Let LeBron just walk, they're going nowhere and committed to $48 million next year, with commitments to Jamison/Williams for two more years, Daniel Gibson for three more years, Varajeo for four more years.