Broadband modem rental fees are usually around $8 per month regardless of provider. Although it is cheaper in the long run to buy your own modem, most people would rather simply pay the fee each month to not have to fool with it which is exactly what ISPs like Comcast want you to do.

As it turns out, modem rental fees are an absolute cash cow for ISPs. A recent Forbes article estimates that a staggering 90 percent of Comcast's broadband customers rent their modems.

Doing a bit more math, the publication surmises that cable modem rental fees contribute between $275 million and $300 million per quarter to Comcast's bottom line. And if recent rumors in the DSL Reports forum are accurate, the monthly fee could be increasing by $2 in the not-too distant future.

The good news is that you can avoid this monthly rental feel altogether simply by supplying your own modem (if you haven't already). They're readily available at retail stores like Best Buy, Target and Wal-Mart or online at any number of sites. A basic modem will set you back around $80-90 which, while more expensive up front, will certainly save you money after the first nine months.

If you're really curious as to the potential cost savings, just do the math based on how many years you've been paying the rental fee.

And if you do decide to go the DIY route, be sure to check your bill each month thereafter to make sure your ISP doesn't try to sneak the fee back in.

Image credit: CNET