The most common question about Sandy Springs plans for a future city hall – how much taxpayer money will it cost? – is the one that’s the most difficult to answer.

City Spokeswoman Sharon Kraun said the city does not have a definitive timeline or budget for the project and said that will become clear when Boston-based firm Goody Clancy finishes drawing the city’s downtown master plan.

In the absence of real numbers, guesstimates and estimates abound. But there are a few established costs.

In 2008, the city paid $8 million for the Target property at 235 Johnson Ferry Road. The city also has $9 million in its so-called “City Hall Fund.” The city set aside $300,000 to pay Goody Clancy, and kicked in an additional $50,000 in grant money.

That means the city already has $17.3 million tied up in the project.

The two undetermined costs will likely be the largest: buying the adjacent property around the Target site and building the city hall.

The city already received some estimates about the cost of buying adjacent property. In 2008, its appraiser did a preliminary estimate of 11 parcels and determined they would be worth $7.35 million, plus or minus 15 to 20 percent. The economy is different today and the some of the owners of the property the city wants aren’t interested in selling, which could jack up the final price if the city takes these parcels using eminent domain.

The cost of building is even harder to gauge. Larry Young, a city judge and president of the Sandy Springs Council of Neighborhoods said during a March 22 meeting that he looked at information related to the building of nine city halls in the metro area. He said costs ranged from $9 million to $50 million.

“It depends on how big it is,” Young told the Council of Neighborhoods.

Jan Saperstein, owner of Sandy Springs Plaza and a member of the Main Street Alliance, thinks he has the cost figured out. He thinks it will cost $20.6 million.

Saperstein presented his estimates during the March 22 meeting to help him make the Main Street Alliance’s case that the Target site should be a park and not a municipal complex.

Saperstein’s estimate assumes the city will build a 75,000 square foot, two-story building. It excludes the cost of the land the city already purchased. His estimate includes $1.6 million in site preparation, $3 million for a parking deck and $1 million in interior improvements.

Saperstein, whose job involves developing and leasing commercial real estate, said he would have a hard time getting the financing for a project like the one the city plans.

“If we were building this today ourselves, it wouldn’t get built,” he said.

Assuming Saperstein’s conclusions are accurate, adding that to what the city currently has invested in the city hall project, the cost would be $38 million.

But nothing is certain. All of these estimates assume the city hall will be built on the Target site. Goody Clancy’s report could suggest an alternative plan. The firm has promised to keep an “open mind” when deciding where the city hall should go.

Dan Whisenhunt wrote for Reporter Newspapers from 2011-2014. He is the founder and editor of Decaturish.com