Thank you Sabyasachi for the information. I think the price is very high almost same as the primes Canon 400mm f/2.8L, 500mm f/4L, 600mm f/4L. I am sure the quality cannot be equated with these primes but the flexibility of zoom will be helpful to many people working at super zoom level. If it is compatible with 2x extender then that will be an added advantage but then again the aperture and quality is a matter of concern.