The most I would pay for any Japanese made machine (with only a few rare examples) is $50. For that I would expect the machine and case to both be in top condition. They're just too common to have any real collector value.
If I don't see one at a price I want today all I have to do is wait and another one at a price I do like will show up.
Prices on old sewing machines are low for good reasons. The supply far exceeds the demand on common models.
Japanese 15 clones were made by the millions after WWII.
For people that have already bought a couple machines condition becomes very important both cosmetically and functionally. I've only been doing this for a little over a year. I have over 20 machines. If I want a project I don't need to leave the house. I've got plenty already.
Rodney