How much money a third observation deck in Chicago might generate

Potential buyers of the Aon Tower in downtown Chicago are looking into making money through the addition of an observation deck:

A third observatory could generate tens of millions of dollars in annual revenue for the 1,136-foot-tall office building overlooking Millennium Park. The building, owned by Johns Creek, Ga.-based Piedmont Office Realty Trust, is attracting bids above $650 million, people familiar with the sales process say…

It would cost millions of dollars to design the space, to create an entrance and elevator access separate from those used by office tenants, and to promote and operate the observatory. Plus, unlike in most cities, two formidable competitors already are in place.

“It’s not a build-it-and-they-will-come type of operation,” says Randy Stancik, who has been general manager of the Skydeck for 10 years after eight years at the Hancock’s observatory. “You really have to work at it to build a visitor attraction. You have to be prepared to stay with it through some rough times.”…

There is little precedent to indicate whether a third observatory can thrive here. New York is the only city in the world with three, says Daniel Thomas, executive director of the World Federation of Great Towers, a group dedicated to generating tourism for its 49 member towers. New York has the Empire State Building Observatory, Top of the Rock at Rockefeller Center and the recently opened One World Observatory atop the new One World Trade Center.

This could be another front of the ongoing Chicago-New York City feud: could the two cities have an equal number of observation decks?

I would guess the Aon Center could have two major selling points compared to its competitors:

1. A different location. The Sears Tower deck is quite good for looking out into the suburbs but its views to the east are filled with buildings. The John Hancock observation deck offers different views to the north and over Lake Michigan. But, the Aon Center would be the only one with unobstructed views of Millennium and Grant Parks.

2. It is the newest. This may not mean much these days with a sort of arms race between the other two observation decks: the glass floor protruding deck at the Sears Tower and the Tilt at the John Hancock. I imagine the Aon Center buyers could come up with something unique that could attract people.

Perhaps this could lead to some sort of price wars between three observation decks leading to great deals for visitors…this is something I imagine people could get behind.