$850 is too much. Several recent Ebay completed auctions in the $499-$599 range. One Buy It Now went at $699, but $850 is too much of a premium for the card.
Concentrating on my personal collection. Please drop me a PM if you have any of the following for sale: Topps Football 1956-1959; 1961-1968; Philadelphia Football 1964-1967, Autographs of Baseball/Football Vintage Stars and Hall of Famers (especially on card autos), 1990's Topps Chrome Refractor Inserts of all sports.