video vs still camera lenses
A pro video camera is almost never used hand-held, so size an weight is rarely an issue. Video lenses generally need greater zoom ranges, often at rather fast apertures to maintain good DoF control all over the range.
i.e. Canon 30-300 f/2.9-3.7, at 13lbs (about 2x the weight of a 500mm f/4), costs about 45k - impractical for stills, more efficient and cheaper to get a pair of 1D bodies with a 24-70 and a 70-200, and maybe a 300 f/2.8.