My game dealer takes the view that, in my case at least, about 40% of the carcasses I take in will have been head/neck shot. I believe he takes an 'average' view and gives a middle price between head and chest shots. A broadly similar percentage of the carcasses I see in his chiller are also head/neck shot.
Encouraging head/neck shots with more money encourages hero long distance shots, with the dangers we are all familiar with - I know he rails against that, and good on him for that.
FYI all kangaroos culled for the commercial meat market
must be head-shot in Aus. There tests are
Their shooting test and calibre requirements:
Most of this is culling done at night, which is ironic given the 'Best Practise Guidance' we have here in Scotland, where head and neck shooting under the (usually Aus made) lamp is barred. (Or should I now say Chinese NV/Bulgarian-Serbian thermal?)