Some US money market funds are charging investors excessive fees, analysts say. And despite historically low yields and investors piling into these cash management products in droves, prices well above the industry norm have gone unnoticed.

Since most money market funds compete solely on their yield, little attention is paid to the fees customers are paying. An estimated 98 money funds, net of waivers, are charging more than 1 per cent of assets and more than 200 money funds are charging 0.80 per cent or higher. The average expense ratio on a money market fund is 0.58 per cent, according to Morningstar.