The Boeing Co. is paying $23.35 million to buy three North Charleston office buildings from the South Carolina Research Authority, a next-door neighbor of the company’s local campus.

SCRA CEO Bill Mahoney disclosed the price Thursday, after the sale was finalized.

The Post and Courier reported the sale this month, but the price remained a secret because the aerospace giant required the state-chartered non-profit authority to sign a non-disclosure agreement. That confidentiality clause expired when the deal closed.

“We had an appraisal, Boeing had an appraisal, we split the difference and we arrived at a price,” Mahoney said, calling the agreed-upon figure a “fair market value as far as we’re concerned.”

The buildings, which total 178,000 square feet, are on about 20 acres owned by the Charleston County Aviation Authority between the Boeing South Carolina campus and International Boulevard. They were built in 1989 and appraised at $25 million in 2010, an SCRA spokeswoman said last week.

Boeing officials have said the company, which makes 787 Dreamliners in North Charleston, has no immediate plans for the buildings, but that they allow for any future growth.

Mahoney noted that while the SCRA, at Boeing’s request, received approval to transfer its ground lease in September 2010, negotiations to sell the building did not begin until August.

“It was something that we did in short order but with a lot of care for a couple of reasons,” Mahoney said. Not only was it “an important transaction for both companies,” but also the SCRA has had contracts with Boeing’s defense division for 24 years, including five right now, Mahoney said.

“We’ve had a satisfactory relationship with those guys for a long time,” he said.

In addition to that delicate circumstance, the chairman of the SCRA board is none other than a top Boeing executive, Marco Cavazzoni.

Cavazzoni, who was appointed to the board by Gov. Nikki Haley last year, was Boeing South Carolina’s second-in-command until three months ago, when he became the plane-maker’s vice president of supply-chain management and operations for Italy.

Cavazzoni “removed himself physically” from the board discussions of the deal, according to Mahoney, and otherwise recused himself.

“Both companies were very mindful that we needed to be very careful with Marco’s recusal in this,” Mahoney said.

The SCRA, which has more than 100 local employees there, will remain in the complex as a tenant, and serve as landlord to the other tenants, such as the College of Charleston’s Lowcountry Graduate Center, the Charleston Trident Association of Realtors and the Charleston Regional Development Alliance, for the next two years.

Reach Brendan Kearney at 937-5906.