The announcement that a group led by William Chisholm agreed to pay $6.1 billion for the Celtics, the highest price ever for a North American sports franchise, raised a big question: How did Chisholm make all that money?

Chisholm won’t have to pony up those billions all alone. He’s leading a consortium of other fabulously wealthy people who are chipping in, but even a portion of the eye-popping figure would be unattainable for all but the richest Americans. And like many of those people (including Celtics co-owner Steve Pagliuca), Chisholm made his fortune in finance, investing in mergers and acquisitions.

After growing up in Georgetown, attending Dartmouth College, and working at a Wall Street firm, Chisholm joined corporate consulting giant Bain & Co, the same firm where Pagliuca worked early in his career. And like Pagliuca, Chisholm pivoted from consulting to the more lucrative niche of leveraged buyouts, joining California-based Symphony Technology Group in 2002.

Buyout firms aim to acquire companies largely with borrowed money, improve operations and cut costs, then resell within a few years, often at a massive profit. The firms can use revenue from a company they purchased to pay back debt and then sell the improved holding for more than they paid. It doesn’t always work out — sometimes buyout firms use too much debt and wreck companies, like Steward Healthcare or Red Lobster, which ended up in bankruptcy.

Symphony, founded by tech billionaire Romesh Wadhwani, has a different model. The firm started out focusing on acquiring small- and medium-sized software firms and delving deeper into company operations than most buyout firms. And Symphony typically owns its companies for longer than most buyout firms, sometimes for 10 years or more.

The firm’s team includes people who worked at, ran, or consulted for software companies, Chisholm said in a 2016 interview with TheStreet.com.

“Our approach is ultimately to build a great company and the return and exit will follow,” Chisholm said in the interview. “Of course, we do have an eye toward what kind of exit this could potentially be, but we are more focused on what company we can build. Our DNA as a team is more centered around business builders rather than financial engineers.”

While larger tech-oriented buyout firms like Silver Lake, Thoma Bravo, and Vista Equity Partners make acquisition deals valued in the billions of dollars, Symphony has more frequently spent a few hundred million dollars. But it often parlays those comparatively smaller deals into massive returns.

In one typical deal, Symphony bought First Advantage, which makes software for background checks and other hiring needs, in 2010 for $265 million. In 2019, it sold the company to investment firm Silver Lake for a reported $1.5 billion. It bought engineering software firm MSC Software for $360 million in 2009 and sold it in 2017 for $834 million.

Symphony sometimes seeks to cheaply buy companies that have run into problems. E-commerce site Shopzilla was languishing under the ownership of publisher E.W. Scripps, which had paid $525 million for the company in 2005. Symphony bought it for $165 million in 2011, made numerous changes and acquisitions, and sold the company, renamed Connexity, to online ad seller Taboola for $800 million in 2021.

Lately, Symphony has been increasing how much it spends in each deal. In 2020, the firm led a group of investors that bought encryption pioneer RSA from Dell for $2.1 billion. In 2021, it paid $4 billion for part of McAfee’s cybersecurity business. And in 2023, Symphony bought local video software firm Avid Technology for $1.4 billion.

Sometimes the improvements include cost-cutting. At Avid, based in Burlington, Symphony cut an undisclosed number of jobs last year.

For all the money-making deals Chisholm has made in his career, the lifelong Celtics fan might struggle to match the returns of the team’s current ownership group, led by Wyc Grousbeck.

Grousbeck’s group, which paid $360 million for the team in 2002, is making almost 17 times their initial purchase price on the deal (excluding the cost of debt and any money the group subsequently invested).

For Chisholm to match Pagliuca on that deal, he’d have to find a buyer willing to pay more than $100 billion.

Aaron Pressman can be reached at [email protected]. Follow him @ampressman.