The Vanguard Target Retirement 2035 Fund reported an expense ratio reduction of 3 basis points, while the remainder of the series of 12 Vanguard Target Retirement Funds reported reductions of 2 basis points.

The expense ratios now range from 0.14 percent to 0.16 percent. In June of 2015, Vanguard launched a separate series of 12 institutional target-date funds with lower costs (0.10 percent) and higher minimum investment requirements ($100 million).

Vanguard also reported expense ratio reductions for a range of fund share classes (Investor, Admiral, ETF, Institutional, and Institutional Plus) for the 12 months ended September 2015, in four other fund categories:

• actively managed balanced

• fundamentally managed active equity

• quantitatively managed active equity

• bond index

Fund fees in general have been under heavy downward pressure, not that that's meant less revenue, according to a Morningstar report last year. And it's not just clients—both retail and institutional—who are looking for lower fees.

Just last October FINRA ordered five firms to pay restitution to retirement account clients and eligible charitable organizations after they failed to waive mutual fund fees. And that was after a July order from FINRA to five other firms for the same thing.

Vanguard has not been shy about its own cost-cutting measures and the reasons for doing so. "The compounding effect of high costs is especially corrosive to the returns of retirement investors—those saving over 30 to 40 years in a 401(k) plan or through an IRA," Bill McNabb, Vanguard CEO, said in a statement.

He added, "As a result, low costs, along with high savings rates, are critical to the retirement readiness of millions of Americans."