Politicians say conventions expose outsiders to St. Louis and create a bustling downtown while also boosting taxes.

“It’s not really about the cost of operating a facility, or for that matter, building a facility,” Ratcliffe said. “It’s about the return on that investment.”

Commission leaders estimated that the Meeting Professionals International delegates, for instance, spent $6.5 million here. Within two years, the convention center sales team had booked 10 new meetings, representing about 7,000 visitors and 18,000 nights in area hotels, thanks to the planners. Leaders declared the convention a “great success.”

But the new business had a cost: The four-day event that July weekend in 2012 totaled more than $1.5 million, half of which was covered by taxpayers.

Meanwhile, the Visitors Commission loses millions of dollars annually. St. Louis and St. Louis County send the agency more than $16 million a year for operations, plus $33 million for debt and upkeep on the downtown convention center and domed stadium.

The taxes dedicated to covering those costs — 7.25 percent in hotel taxes in St. Louis city and county, plus a 1 percent restaurant tax in the city — fall short by a few million dollars a year.