Sewing machine prices vary greatly by area, collectors and of course condition. The pink and aqua and such usually fetch a slightly better price. But in general, there isn't nearly as much a market for vintage machines (and therefore lower prices) than you may hope/expect. Personally, I'd rather buy a good vintage metal machine over just about any plastic computerized machine, but I seem to be in the minority.
For your area prices, start looking at Craig's List or similar. Internet sites including auction sites like Ebay and the marketplace at Amazon.