Motorola Surfboard SB5101 Cable Modem for $37.99 shipped.  Here is a screenshot for your reference.  It is also available here for $39.02 shipped.  Note that this modem comes in OEM packaging, which means no pretty retail box and marketing materials but is otherwise identical.  Having a cable modem often means you will not have to rent an Internet cable modem from the cable company, but it is important to check with your ISP to ensure that this is a compatible model.  As a comparison, Best Buy has this cable modem for $79.