Having decided I will stick with my D7200 & Sigma 150-600 for now and that my best option in the future would be a D500 & Nikon 500 mm PF. So being on a tight budget I have been looking around, always good to keep an eye out for a bargain, also read a few reviews of the 500mm PF, all seem favourable, so why so many for sale ? A fairly new lens on the market, very much sort after originally and yet now there seems to be masses for sale? and the prices vary widly ! Anyone shed anylight on why so many are up for grabs ?