Christian Anschutz, who bought the property from the Denver Technological Center, plans a $100-million mixed-use development on his land. Sullivan, for his part, sold three buildings and a parking garage for about $37.5 million. Sullivan says the development has about 97,000 sf, although an offering package from CB Richard Ellis Institutional Group a couple of years ago put the sf at 81,568 sf of office and 18,657 sf of retail, as well as a 276-car parking garage.

Either way, the price per sf eclipses the previous record, when the Janus building sold for about $364 per sf. The Janus building is about a block from the property Sullivan sold.

Mary Sullivan (no relation to Jim) listed the property for Sullivan a couple of years ago, but didn't sell it. She says Sullivan renovated the buildings, including the former Catholic Archdiocese headquarters; the way a person would renovate a mansion. His bet that people would pay for quality paid off. Rents in Sullivan's property far out-stripped buildings a few blocks away, she tells GlobeSt.com. The purchase also includes a building completed in 2002, which includes Mao Asian Bistro and Sushi restaurant, which Sullivan owns.

Sullivan tells GlobeSt.com that he considers the buildings "generational properties," which could be passed down to family members. Indeed, that was his plan.

"It was an unsolicited offer," Sullivan tells GlobeSt.com. "The buyer told me he really wanted these properties. I told him they weren't for sale. He kept coming back to me, until he offered me a price that I couldn't refuse."

Sullivan recently sold his retail brokerage firm SullivanHayes Cos. to former tennis pro Michael Chang's family business.