How Much is Your 401K Costing You? [AUDIO] By Kelly Waldron | 9 July, 2012 - 4:41 pm |9 July, 2012 401 (k) Retirement Plans You may not realize it, but hidden fees could be costing you up to 30 percent of your 401k plan over time. A new federal rule, that went into effect. Read more: How Much is Your 401K Costing You? [AUDIO] Tagged may-not, new-federal, plan-over. Bookmark the permalink.