Commission skirmishes steal headlines, but fund expenses remain the largest battleground in the discount brokerage price war as firms attempt to capture more assets down-market.

In March, Charles Schwab Investment Management eliminated investment minimums on all of its index mutual funds.

Previously, Schwab moved to a single share class that does not differentiate between account balances. Across the index mutual fund industry, share classes with graduated mutual fund fees are commonly used—expenses decline as account balances increase.

Any investment in Schwab’s S&P 500 Index Fund (SWPPX), for example, carries a 3 basis point expense ratio, regardless of dollar amount.

“The lower cost is important because of the power of compounding over the years,” says Jonathan de St. Paer, Schwab senior vice president for business strategy and product development. “A handful of basis points makes a big difference over the long term.”

Schwab’s S&P 500 fund is now cheaper than similar funds at Fidelity, which charges 9 basis points for low-balance holdings, and Vanguard, which charges 16 basis points. Schwab also beats Vanguard and Fidelity expense ratios for total market and large-cap core mutual funds at all asset levels.

Vanguard and Fidelity still match or beat Schwab’s pricing for small-cap core, international multi-cap and inflation-protected funds. Yet Vanguard and Fidelity require minimum investments—$3,000 for Vanguard’s mutual funds and $2,000 for Fidelity’s.

ETF purchases at Fidelity and Vanguard come with no minimum, noted a Vanguard spokesperson, and ETF expenses are not pegged to account balances.

“I think our price options and minimums have been competitive and adaptive over the years,” says Bob Litle, head of intermediary sales at Fidelity. “We’re watching what our competitors are doing to find opportunities. I don’t think it’s the case that the best investment is always the one that charges the least, though.”

Investors’ focus on fund pricing may go too far, says Vanguard. “We agree that the ‘How low can they go?’ fee compression story is a bit played out,” said a Vanguard spokesperson via email. “It’s like cost has become the ‘new performance,’ and some investors may be mistakenly making investment decisions based solely on that one factor.”

Litle says advisors also should avoid being too price conscious, even though they may believe that finding the lowest cost investment solution is the easiest way to fulfill their fiduciary duty to their clients.

“The Department of Labor has indicated that a fiduciary is not obligated to offer the least expensive things to their clients,” says Litle. “If you just offer the cheapest thing available, you’re probably not doing as much for your clients as you should when it comes to selecting investments.”

Vanguard’s spokesperson pointed out that for most investors averaging into an investment, the impact of one basis point in fees over a 30-year period only amounts to a few hundred dollars, while other decisions, like savings rate, allocation, asset location and investment discipline have bigger impacts.

Advisors and investors should examine their investments’ after-tax performance—an area where Vanguard’s funds tend to be superior to those from Fidelity and Schwab when total returns are considered.

“The final consideration should be looking at complex-wide costs,” said the Vanguard spokesperson. “Many investment houses promote loss-leader index and ETF products, but when you look at the rest of the fund family, you’ll see considerably higher expenses.”