They see 75,000 people shelling out for tickets, beer, and hot dogs and consider that economic growth. No thought for what the money might have otherwise been spent on.
On the other hand, any sports venue that attracts large numbers of people from outside the region actually does provide huge economic benefits for the region. Just ask anyone who runs a business in Daytona or Talladega when a couple of hundred thousand people travel to the area during the weekend of a NASCAR race, or anyone who runs a business near Churchill Downs during Kentucky Derby week.
One way the NFL helps individual teams "inflate" the economic benefits of these new stadiums is by promising them a Super Bowl within the first few years after the stadium opens. This is why Jacksonville hosted a Super Bowl a few years back even though it was totally unsuitable for that sort of event, and why the new MetLife Stadium in the New Jersey Meadowlands is going to host the Super Bowl in a couple of years even though NFL policy doesn't allow outdoor Super Bowls in that kind of climate.
I recently went to a SF Giants game with my brother in law and sister in law and their son. The park is beautiful, the food was priced a little high, but in line with the pricing I see at fairs.
Tickets, granted I was six rows up from the first base line, but those tickets were $110 each! Luckily he got the four tickets for free because I would hate to think that he would shell out $400 plus for baseball tickets.
I think the cheap seats were $45.
And that is what is wrong with professional sports.
Now down in San Jose there is the minor league SJ Giants. Ticket prices are very very low, (few dollars), they give away chicken dinners between innings, nice family atmosphere, and not a bad seat in the house.
It is all just entertainment.