While it is most difficult to arrive at actual figures it is estimated that in New Orleans Mardi Gras is close to a $100 million dollar boost to the city's economy while the Mobile figure is nearing $30 million.
Just one illustration may make the point of how much Mardi Gras means to the economy. In Mobile alone there are approximately 50 Mardi Gras Carnival balls each year requiring formal attire. If each of these balls average 1000 guests and members (Naturally some will have fewer while others up to 4,000 in attendance.) and half of these attendees are ladies, this will result in 25,000 ball gowns being needed each season. Erring on the conservative side, let's assume that only half of these attendees buy only one new gown each year and that each of these 12,500 new gowns cost only an average $200 each. That's a conservative $2,500,000.00 alone per Mardi Gras season - just in Mobile.
And before someone says or thinks - what a waste of money. These people could be putting that money to better use. Yes, perhaps this is true. Money spent on movies, or on golf could be put to "better" use, but that is just the point. This money is discretionary money - funds which, if not used on Mardi Gras would be used for golf, movies or an extended vacation- or even perhaps for a trip to the coast gambling casinos. So the argument, while perhaps valid, is moot.