Many walmart stores have this Arris surfboard cable modem on clearance for as low as $9. The retail price is $108! YMMV. This is a great deal for a cable modem that includes a 4-port gigabit ethernet switch and wifi. I was able to pickup several for $21.
It's widely available so I dont think many resellers know about this yet. If you want it better get it quick before the resellers sweep all the local walmarts and buy all the stock.
ARRIS SURFboard SBG6580 DOCSIS 3.0 Cable Modem [walmart.com]
- link is for reference only you need to buy in store
You dont need to use brickseek. I checked the price at 3,702 walmart stores and put the prices at the below google spreadsheet. You can sort by city, state, zip.