nikon 80-400 is too expensive.
compare some of the more or less competitive lenses
nikon 80-400 4,5-5,6 G ED VR 2800 eur
nikon 70-200 2,8G ED VR II 1800 eur
sigma 50-500 4,5-6,3 DG OS HSM 1400 eur
sigma 300 mm 2.8 EX DG HSN 3000 eur
sigma 120-300 mm 2.8 APO EX DG OS HSM 2000 eur
More expensive than 70-200 2.8 VRII?
Twice better than bigma?
The real price should be under 2k eur