We have been broadcasting all of our school's games for 3 years now on Youtube and Facebook. What we have found is that we are drawing in more casual fans and other people in our community who wouldn't normally go attend games in person. This includes teachers, elderly people, and those with large families of small children. Our ticketed attendance has been relatively unchanged (excluding this year). The only time that we have seen poor attendance due to a livestream is when the football team is playing in terrible weather.
Instead of charging people to watch, we just asked for donations. That way people could donate if they wanted, but didn't feel obligated. They also didn't have to get a credit card out for every game, just to pay $10 to watch a 50-0 blowout. This also ensured that 100% of the proceeds went back into the athletic department, rather than 50% that most PPV platforms do.