3/4 sized treadles are about as rare as hen's teeth in most parts of the US. That's about the same as I paid for mine - which isn't even an original Singer treadle. Mine has a square "breadbox" or "coffin top" but I think the decals are the same as the ones you have here - they're called "Victorian," I think.
I think it's a very good deal. And if it didn't come with attachments or bobbins, it's very easy to find parts for. Try to buy only vintage bobbins for it - the modern repros are a little short, so you have to guide the thread by hand. If the longer vintage bobbins are used, the machine will fill the bobbins evenly and automatically.
Have fun with it - they're wonderful machines. Some people like quilting on the vibrating shuttle machines even more than on the 15's. :)