For me it's simple, £/KG is XYZ, pickup areas are such and such with X amount of notification required. Carcasses need to be in such and such condition, extra payments will be/or not made for tails, pizzles, pluck, etc. Payments are made via cheque/cash/direct credit within X timescales.
If these details are not there and not public for anyone to know about, then I'd personally prefer to drop deer off in a place where I can go knocking on the door if money isn't coming through. I know that's a luxury problem because in loads of places you simply don't have a decent game dealer near you, but I have at least two good one's within reach, so I'd need a heck of a good price per KG to go elsewhere. FWIW, for Roe, I would need £3.20 to go elsewhere, and for reds £2.80 along with money for tails and pizzle (tails go to chinese medicine of course! so do the boys toys,,yuck..)..