You have 8 sewing machines, 2 of them industrial, and no patience for repairing machines. I guess the key question for me is, why do you buy sewing machines? It can be an addiction just like anything else, with no real ongoing value for *you* of the things collected.
I used to collect vintage sewing machines. Just loved fixing them up, the nostalgia associated with them, etc. Finally one day my husband asked me if I ever used any of them, because they were taking up a lot of floor space. I got to thinking about it, and realized that I never used them because for "real" sewing I actually preferred my Bernina 1230. It was always reliable, never needed adjusting, was always ready to go when I needed to do something, the low hum of the machine was soothing, and I simply always enjoyed using it. I loved the vintage machines in terms of having them, but did not love using them.
It was hard, but I put an ad in the paper and found another collector who came to the house and bought most of my vintage machines (gave her low reasonable prices on everything). I kept a few that had sentimental value.
I'd still love to buy a treadle machine, but I won't unless I become sure that I will use it on a regular basis. I know from experience that vintage machines can become dust collectors.
When I was collecting, I did pass up a couple of great thrift store buys and was haunted by them for awhile. I think this is one of the costs of addiction. At that time, while still in the throes of collecting addiction, I think I should have bought them. Now it would not bother me to pass these machines up and let someone else have the thrill of "the find".