With investment costs, less is more. Many investors are getting the message that paying less for mutual funds (or for any investment, really) will put more money in their pockets in the long run.

Last year, investors in the United States paid, on average, the lowest mutual fund fees ever, according to Morningstar.

But investment costs are full of unpleasant surprises, and academic studies have found that many people aren’t taking advantage of better-priced alternatives.

“In one part of the market there is enormous cost competition, and investors there have never had it better: They can buy funds almost for free,” said Micah Hauptman, financial services counsel with the Consumer Federation of America, a nonprofit research and advocacy group.