$50 would be a little high for me; $30 would be more reasonable. I would want to know what condition the cords are in, though; I don't like having to fool around with the electrical components. I would also expect the bobbin case to be included (replacements cost about $25 online) and the machine to actually sew.
Oops! I see it's a handcrank. I might pay $50 for a handcrank. It looks like it's a handcrank that has been "updated" for electrical use as well. $40 would be better.