Newegg offers the refurbished Motorola Arris Surfboard 600 Series DOCSIS 3.0 Broadband Cable Modem, model no. SB6183, for $54.99 with free shipping. That's tied with last week's mention and $45 under the lowest total price we could find for a new one. It features download speeds of more than 600Mbps and upload speeds of more than 100Mbps.
A 90-day warranty applies, but it's not clear who backs it.