Either the UFC $4B valuation is way too high, or Disney stole the Star Wars franchise from Lucas films. The disparity in revenue on a historical or annualized basis is huge.
Consider another way: had Disney not bought Star Wars, do you believe they could have built a franchise or franchises of a similar money-printing status for that $4bil? Pirates of the Caribbean have earned close to $4bil:
http://www.boxofficemojo.com/franchises/chart/?id=piratesoft...
UFC is a running institution that other parties work to endure and build. Gyms find and train fighters (UFC does not need to participate in this). Those Gyms hype fighters and build fanbases that feed back in as a tributary to UFC. 8x rev for a quickly growing sport franchise that essentially 'owns' fighting outside of Boxing is not terribly high a valuation.
The value of Lucas to Disney is much higher than the $4B price tag either Lucas or UFC yielded, but a lot of that stems from Disney's amazing ability to execute on it. UFC seems more capable of standing alone as a business.