Here's the money (ha) quote:
With more than four decades of evidence to back them up, economists almost uniformly agree that publicly financed stadiums rarely pay for themselves. The notable successes like Camden Yards in Baltimore often involve dedicated taxes or large infusions of private money. Even then, using one tax to finance a stadium can often steer spending away from other, perhaps worthier, projects.
We're all huge sports fans, obviously, but we have to stop supporting public money for stadiums that largely create private revenue, at a net loss to the taxpayer.
The myth that the stadiums pay for themselves needs to be killed off forever.