There is one simple rule. When only .com is registered (I am just guessing) Than concerning keywords you can make 2 conclusions.
1. There is not much competition on those.
2. The domain gets 0 type in traffic. (when its a generic typo this could be untrue)
All those domains fitting the criteria from above are worth anything between X - XXX USD, for a right end user. (but you have to be extremely lucky to get XXX.