I bought a broken lifetime 648 with wi-fi adapter and remote on Craigslist for $30. I fixed it and sold it without the remote for $100. I made a little bit of money and got a remote out of it.
I started at $200, and kept lowing the price every two weeks. Took 2 months to sell. The problem with the 648 is that its not compatible with MP4 that cable companies are switching to and I didn't feel comfortable selling to someone who want to use in with cable.
It took 2 months to sell for $100 to someone that wanted to use it with OTA.
S2(03/2006), S3(10/2006) (OTA), TiVo Hd(04/2010), Premiere(05/2012) (OTA), Roamio Basic (11/2013)(Comcast Cable).