The fine of $50,000 -- which Darren Rovell points out is equal to roughly four-and-a-half minutes of game play for Favre -- is not for violating the league's personal-conduct policies though. Instead, Favre is being fined because he didn't cooperate with the NFL's investigation into whether or not he sexually harassed Sterger.
On the basis of the evidence currently available to him, Commissioner Goodell could not conclude that Favre violated league policies relating to workplace conduct. The forensic analysis could not establish that Favre sent the objectionable photographs to Sterger. The review found no evidence to contradict the statements of both Favre and Sterger that they never met in person, nor was there anything to suggest that Sterger engaged in any inappropriate conduct.
However, Commissioner Goodell also determined that Favre was not candid in several respects during the investigation, resulting in a longer review and additional negative public attention for Favre, Sterger, and the NFL. The commissioner notified Favre that he has been fined $50,000 for his failure to cooperate with the investigation in a forthcoming manner. Commissioner Goodell stated to Favre that if he had found a violation of the league's workplace conduct policies, he would have imposed a substantially higher level of discipline.
This means that Favre can play in the Vikings' season finale at Detroit on Sunday, assuming he passes the concussion tests.