I think it also depends on where you are located. I have three treadles, all coming to me in very nice condition, cabinet and machine...my Minnesota A...free, my Singer 15-88, $40 and my newest Singer Godzilla 66 $30. But you have to be patient and look and sometimes quick! Also be prepared to negotiate. My 66 was originally advertised for 3x what I paid. I live in Midwest and assume east coast etc are higher priced but you know what happens when you ASSume.
