I had a chance to watch the HGTV show "Cash In The Attic" this morning where the host and an "expert" pick items from a family's possessions and takes them to auction to raise funds for a specific purpose or project. One of this morning's possessions was the lady's Grandmother's Singer sewing machine. The machine lived down in the basement, the finish was dull or extremely dirty and it was covered with cobwebs. Probably frozen solid from being in the damp basement for a prolonged period, too. It was a 15 Class machine, I think a 15-91 but I didn't get a good look at the backside to be sure. The "expert" asked the owner what she thought it was worth and she immediately said, "$400 to $500". The "expert" explained that everyone has a Singer sewing machine, they aren't rare and estimated the value at $50. Needless to say, the owner was considerably deflated, seeing her bathroom remodeling going up in smoke. I was a bit skeptical at the $50 estimate because I have never paid more than half that for a 15-91. It sold at auction for $5.
I run into this all the time - people visit antique shops and see treadle machines marked at $250, then think that because they have a similar black Singer with gold decals, theirs has a similar value. It just ain't so.