I purchased the 600 f/4 a while back and the 500f/4 is not used any more. I will be putting the money towards a NEW 400 f/2.8. It is complete with all accessories as from Canon plus 2 lens coats (winter) (fall) colors.
It is in excellant condition and only a few years new. I send my big guns in every year to Canon for check ups. Price is $ 5,000.00 plus shipping to lower 48 states only.