I have two Featherweights (FW). Value is hard to assign because there are several factors to consider. I think the biggest factors are condition of the machine AND the case. No case significantly decreases the value. The machines came with a set of feet as well, they should all be there. I think there is more demand for the scroll faceplate (which you probably have). The bobbin case is another big expense to replace if one is missing.
I can only speak for myself, but I prefer selling locally through Craigslist or Facebook Marketplace, with cash, at a lower price than deal with shipping and collecting the money online.