Here are two papers on super bowl and stadium financing impact by someone with no stake in game
http://college.holycross.edu/RePEc/hcx/Matheson_SuperBowl09.pdf
His finding The Super Bowl is America‟s premier sporting event. This paper details basic economic
facts about the game as examines the controversy surrounding the purported economic impact of
the game on host communities. While the league and sports boosters claim that the game brings
up to a $500 million economic impact to host cities, a review of the literature suggests that the
true economic impact is a fraction of this amount.
http://college.holycross.edu/RePEc/hcx/Matheson-Baade_FinancingSports.pdf
Interesting paper on financing of stadium.
Also isnt the same group that estimated economic impact for the marlins the ones that came up with the numbers for the dolphins. I have heard this no exact proof though.
Also on economic impac
PricewaterhouseCoopers has estimated the economic impact of multiple Super Bowls. According to its analysis, direct visitor spending has ranged from a low of close to $120 million in Detroit in 2006, to high of about $200 million in Dallas/Fort Worth in 2011. The firm (which wasn’t paid by the Host Committee) projected $185 million in economic impact for the New Orleans Super Bowl held earlier this year.