Used leather machines don't pop up often, so finding a good deal on a used machine is tough. I looked for almost a year, but I finaly found a good used Consew 206 for $400. Then I spent ~250$ on a servo motor, new needles, thead, and a few mecanical issues. At the time, that machine was 1300 new. Before that, I tried to make an old Singer cast iron machine work, and it just wouldn't do what i needed it to do. Luckily, I cleaned it up real well and sold it to a lady who wanted to use it as a decoration in her house.
Best of luck with your search.