Newegg offers the refurbished Arris SurfBoard DOCSIS 3.0 Cable Modem, model no. SB6141, for $39.99 with free shipping. That's tied with our June refurb mention as the lowest total price we've seen. (It's $30 under the price of a new one today.) It features support for IPv4 and IPv6 and enhanced network management. Note that it may not be compatible with all service providers. Deal ends November 1.
A 90-day warranty applies, although it's unclear who backs it.