The trustees - board members tasked with overseeing AXA funds - had events there and at other ritzy spots, legal records show. A 2011 holiday party at a Del Frisco's restaurant cost $25,775, a $1,000 average for each of roughly 25 people present.
"The wine was very good," a trustee recalled of one meal.
The trustees' dining experiences emerged in a federal case decided in August. Investors including a teacher and a retired police officer accused the firm of collecting excessive fees, a charge the firm denied.
US District Judge Peter Sheridan sided with AXA in his 146-page decision, but he wrote the suit had prompted a "more scrupulous and rigorous" review of board expenses. One result was to reimburse investors for some of the meal costs.
In courts across the land, investors are subjecting mutual fund boards to greater scrutiny. Trustees, often paid hundreds of thousands of dollars a year, are under pressure to prove they have stood up for shareholders in an industry that has $16 trillion under management.
The lawsuits accuse fund boards of missteps such as failing to scrutinise fees or pass along to investors economies of scale as their funds grow with rising markets. The claims illuminate the long obscure role of fund trustees, sometimes known as directors.
Despite their compensation and influence, at many fund families these individuals rarely appear before investors and face few official qualification requirements. Many are current or retired executives, attorneys or academics, much the same as at large publicly traded companies.
Defendants include large fund managers like BlackRock Inc and Pacific Investment Management Co, or Pimco. The fund managers deny wrongdoing. An AXA spokesman declined to comment.
In theory, mutual fund trustees can demand lower fees on the funds or fire the managers who choose the funds' investments. But firings, which investors could see as disruptive, hardly ever happen.
A common concern is that the boards are more focused on following technical rules than looking out for shareholder interests, said Stephen Davis, a senior fellow at the Harvard Law School Program on Corporate Governance.
Fees are a sensitive topic for many actively managed mutual funds, which are losing billions of dollars in assets to cheaper index-tracking funds. Even a small reduction in fees can make a big difference for investors who include many US workers whose savings are in 401(k) retirement plans.
A 2015 Morningstar study showed that while industry assets increased by 143 percent over a 10-year period, fund fees charged to clients fell only 27 percent while industry fee revenue rose 78 percent, showing companies benefiting from the gains more than their investors.