NEW YORK (CNNMoney)

The company an employee works for makes all the difference. Over the course of a 40-year career, workers at some companies lose tens of thousands of dollars in 401(k) fees and earnings -- sometimes more than double the savings lost by workers at other firms, according to an exclusive analysis of about 2,300 company 401(k) plans by FutureAdvisor, an online financial adviser.

Each year, 401(k) savers pay a percentage of their account balance toward administrative and investment-management fees, which are usually included in the calculation of fund expense ratios. As an individual's account balance grows, so do the fees they pay.

When a retirement saver is just starting out, they usually pay less than $100 in fees a year since their balance is low, according to FutureAdvisor. But when the account balance reaches $50,000, annual fees more than triple to about an average of $355. And by the time a person is ready to retire, the fees can add up to several thousand dollars a year.

And some employees may face additional costs, including trading fees and operating fees to help the company pay for the plan.

In addition to all of these fees are the earnings savers could have realized had they not been paying so much.

Related: Find out how much 401(k) fees are costing you

"While [fees are] a small percentage of your balance, it is a huge chunk of your expected growth," said FutureAdvisor co-founder Bo Lu.

An ordinary two-earner household will lose a whopping $154,794 to fees and lost returns over a 40-year career, according to a study released last year by Demos, a New York City-based think tank.

The highest fees are typically at small companies of 1,000 employees or less, where human resources teams have less power to negotiate with financial firms that offer 401(k)s.

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Your employer may cost you $100K in retirement