I think that for me... when it comes to the vintage machines... it's often a matter of just how much 'will to survive' does the machine have. Both my 101 and BU were abandoned for reasons and I'm just far too modest to think that my amateur skills alone were the only thing that brought them back to sewing. That they did come back and sew as well as they do now... seems like a testament to how well they were made to begin with... and I can appreciate that. Seems to be a difficult quality to find these days.
For future reference, you don't really need to go through all that hassle selling old BU's, Novas or Miras. All those strange people and the time lost sewing... Just box them up and send them to: Steelsewing, Next to the Perogi Shop, Pittsburgh, PA. It's just way easier. =)