Walmart offers the refurbished Netgear CM500 DOCSIS 3.0 Cable Modem for $29.99. Choose in-store pickup to avoid the $5.99 shipping fee. That's $15 under our mention from last month of a new unit and the lowest price we've seen. (It's $15 less than the best deal for a new unit today.) It supports 16 download and four upload channels with speeds up to 680MB/s. It's certified for Comcast Xfinity, Time Warner Cable, Cox, and Charter, among others.
There are plenty of great ways to spend your money, but you can safely leave these products on the store shelf.