"That number is comprised of a bunch of different things," said Dan Hubbard, USGA assistant director of communications. "Restaurants, hotels, bed-and-breakfasts, even things like limousines, catering services, money the USGA spends with local contractors and unions to build up everything that you see at Merion, the tents and all that stuff."
While no official number has come out as to how many out-of-towners will visit the area, past numbers can give economists an insight into just how much capital will flow into the area.
"The numbers in terms of room nights, is anywhere from 60,000 to 100,000 room nights that are booked in connection with this event," said Larry Needle, executive director of the Philadelphia Sports Congress, part of the Philadelphia Convention and Visitors Bureau. "When [the U.S. Open] was in D.C. in 2011, which we think it's a good comparison, they booked over 90,000 nights. It gives you an idea of the magnitude of this event at the end of the day.
"Obviously, the numbers are staggering. It's a great opportunity for the fans from the area to experience something like this. Obviously, it has been a long time since a major golf tournament or any kind of global event of this magnitude has come here."
Visitors have flocked from all over the country for the U.S. Open. They have been invited to get in on the action via social media. Special hashtags have been set up on Twitter by the Philadelphia Convention & Visitors Bureau/Philadelphia Sports Congress to help visitors find deals in the area.
While this happens for every U.S. Open, it is surprising just how much money people are spending, given that ticket sales were capped at about 10,000 fewer per day than at the Olympic Club in San Francisco last year. Attendance at Merion Golf Club this week is about 25,000 per day.
"The economy, the general recovery, helps these kinds of things. I think it is a little bit of a rising tide lifts all boats," Hubbard said. "As the economy recovers in this area, people feel that they have the disposable income to spend on a ticket."
Then, of course, there is the mystique of Merion that draws people to the U.S. Open this year. Mark Giuliani traveled from Hanford, Calif., to see the best golfers in the world vie for the national championship.
"This is the greatest golf course in the United States," Giuliani said. "There is no chance that I am going to miss the U.S. Open on a golf course where Bobby Jones finished the Grand Slam or Ben Hogan hit the 1-iron on 18."
Whether it is the draw of Merion, or simply the U.S. Open, people are flocking to Philadelphia, and boosting the city's economy in the process.
On Twitter: @AndrewJAlbert01