The Sixers are "a dark horse, but not a favorite," as they hold two first-round picks and the potential to build a dynamic roster around James, said Michael Ginnitti, Spotrac's founder.
"They're up there in terms of opportunities," Ginnitti said.
Contenders who are reportedly interested in James, including the Los Angeles Clippers, Chicago Bulls and Houston Rockets, would have to unload key players in order to free up enough money to sign him, Pincus said. The Clippers, for example, may not be willing to ship out players such as DeAndre Jordan in order to bring James to L.A.
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Though they also have cap room, the Cleveland Cavaliers—the team James spurned so he could join the Heat in 2010—likely won't lure James back in the near future. Popular speculation has surrounded his re-signing with the Cavaliers, who are building around young star Kyrie Irving.
Unless teams start making moves to clear up cap space, it seems LeBron may stay put. But even if James re-signs with the Heat, Pincus believes his free agency has spiced up what might have been a dull free agent market for the summer.
"It's great for business that he's opting out," Pincus said.
—By Jacob Pramuk, special to CNBC