I think players who get bought out don't sign big deals elsewhere, one because it's common sense for new teams not to shell out $$$ for someone already making $$$, and two because I think there's some restriction against it.
I think Johnson sees it being more profitable staying in BKN. If winning big was a priority I don't think he would've resigned there years ago. The East is LeBron's conference, the West fluctuates (Thunder, Mavs, Spurs, Spurs, GSW coming out of the West is pretty good fluctuation if you ask me). He probably wouldn't have stayed out here if he wanted to really win. Imagine MEM from a couple years ago with Johnson, or even the Mavs. Both teams could've achieved more..hell Memphis could've gone to the WCF without Johnson had Randoplh not been suspended Game 7 vs OKC.