The moral argument is bolstered by a financial one:
The Independent Democratic Conference … released a report [pdf] showing that New York State stands to generate some $391 million in increased economic activity, revenue, and savings during the three years after it is made law.
Using conservative estimates, the report estimated that 21,309 gay and lesbian couples from New York would get married within the first three years. It also estimates that 3,308 couples from surrounding states that do not have marriage equality would travel to New York to get married, as would 41,907 non-New York gay and lesbian couples who would travel to New York for a “destination wedding.”
This influx would be a boon to New York's wedding and tourism industries, which has been hard hit by the current economic downturn. It would also result in increased revenue for New York State through increased sales tax collections, and help for municipalities in increased collections from marriage license fees, local sales tax, and, in New York City, a hotel occupancy tax.
(Hat tip: Laura Nahmias)