I've often been able to find cable modems at Good Will stores in the $3-$5 range. I found an old DOCSIS 2.0 modem a couple of years ago for $5, even after 3.0 equipment was recommended and rolled out for all rental modem customers, but they still activated the 2.0 modem without issue and my speeds held true to the tier I was paying for. About 3 months ago I found a DOCSIS 3.0 for $3 (no power supply)... both were Motorola and used the same PS, so now I'll stop getting the "UPGRADE YOUR CUSTOMER-OWNED EQUIPMENT" emails from Comcast.