These top-of-the-line Superbas are loved by many, even though they need proper loading to work effectively due to their lack of a second wash arm for the upper rack.  KitchenAid described the wash action as "a hurricane in a box."

It's worth selling, but can't imagine it fetching more than $100.  You can post it for sale in the Shoppers Square forum here, or give craigslist a shot.

This KitchenAid was not original to your house, as it dates back to around 1970 or so.