This is a great subject and I love the answers and the help you are giving everyone. I have several old Singers. (Handcrank 127; (2) 301s; a treadle 15-; electric 66; (2) featherweights; 401; 403; 404 plus I'm looking for a 99 (or Spartan) to make into a handcrank. I'm sure I will learn a lot from reading your Vintage Sewing Machine Shop thread.
You wrote: "Personally I never give over $50 for a machine (with the exception of my Singer 12 MOP) but thats just me."
..thank you for saying that. I think that Singer sewing machines are beautiful and sturdy but it seems that uninformed people have inflated the prices to unreal prices. I can understand paying more when you have a machine that is in outstanding cosmetic shape and is in great mechanical shape, but I see people trying to sell machines that are all scratched up and in so-so mechanical condition for over $200. Unfortunately some people are being taken because they think since this is an antique, it must be worth the price. One person claimed on craigslist that "all" singer sewing machines are going for high prices so they expected to get high prices.
A high price depends on many variable including what machine it is and the condition it is in.
I have to admit that I have paid more than $50 for some of my machines, but I always had a good reason for it and I knew what it was worth. I believe I paid $120 for my 401. Everything else was under $100 and several of them under $50. I got one 301 at a garage sale for $5.
It is important for buyers to realize that not all of the Singer sewing machines are worth the same price of a featherweight in great condition or a treadle that looks brand new.