Advertising and prestige are two of the major reasons why networks pay so much for the rights to broadcast certain sporting events. The NFL playoffs, the NCAA tournament, and the Olympics are three of the biggest sporting events on TV (in the United States).
Do the networks make money on these events alone? Occassionally yes, but most likely no. They host these events on their networks to advertise for their own networks shows and coming events. Jim Nantz is probably more tired of reading 'How I Met Your Mother' and 'The Big Bang Theory' ads than we are hearing them.
Do the Masters get higher TV ratings because they advertise during the NFL playoffs? Probably not. What it is doing is wetting the appetites of major golf fans. I doubt an NFL fan who has never watched the Masters before is going to be influenced to watch the tournament because of an advertisement they saw in January.
Also, I believe the first weekend of the NCAA tournament is the best telecast in all of sports. For me it is like Christmas in March.