I have discoverd there are quite a few treadlers using their machines regularly, so it's not just collectors. I suppose a lot of us tend to have more than one machine, and it's hard to say when a collection starts. I wonder how many of us that acutally use our treadles?
I have seen nice condition machines go for $300 (and those are the common 12, 15 or 27) but I have also seen very nice machines go for next to nothing (almost flawless under a layer of dirt, but you don't always know until later). Old machines aren't always easy to sell in a jiffy. The more elaborate decals are (almost) always much more worn for some reaso so it's quite a nice find you have. I guess the age plays in, the additional 30-60 years gives room for a lot can happen to a machine. I have never seen a machine with Sphinx decals in good condition around here, earlier this summer there was a very nice Tiffany model 15, but not flawless, a bit of rust but decals were nice. Worn but still nice often goes for around a $100 in my area, and price doesn't always reflect condition even if it should.
It will be interesting to see what the experts have to say :- )