Ebay completed auctions and KEH's retail prices are generally good value indicators.
But without actually examining the cameras there is no credable way to determine the value beyond that. Storage is not particularly kind to any mechanical device, cameras included. Lubricants dry out or migrate, plastics deteriorate and sometimes fungus attacks lens surfaces. Your cameras could be jewels or parts donors, or anywhere in between.
After looking at the sources mentioned, if you want to go to the next step in getting a value for the cameras, if you can state where you are folks here might be able to recommend shops that could give you an in-person evaluation of condition and value.