I have been to Africa 5 times and each time I have paid money in advance and the remainder after the hunt. Never paid all in advance, never been asked to. That includes buffalo and elephant. If the outfitter had asked for the trophy fees to be placed in an escrow account, I would have had no problem with that given the large sums involved. He didn't but it would have been entirely reasonable.
It isn't about deciding if the hunt was worth it, it is a model of payment that ensures everyone has their incentives lined up. The African model of a daily fee and a trophy fee makes sense to me. In a farm area, the daily fee is modest. In a free-range tented camp, daily fees are higher, commensurate with the work involved. We both have skin in the game. I pay something whether or not we get a shot on an animal, my PH earns more if he finds an animal. I know there are vagaries of luck, but it seems like a fair system to me.
Asking me to travel thousands of miles to an area I don't know and paying full price to someone I've never met for a hunt where the outfitter has no skin in the game is asking for more trust than I have. Wish I weren't so cynical, but I'm not interested in hunting with someone who has no incentive to try to find an animal. And every incentive to book more hunts than he has tags for and avoid animals as much as possible. I'd be vetting the living hell out of an outfitter in that circumstance before I'd even consider booking a hunt paid in full opportunity or not. I'm happy for him to protect his interest by making ground rules: cover minimum x miles/day if needed, full price for shot opportunity (within mutually-agreeable range) whether or not I take the shot, etc. Nobody would pay full price for a house and be satisfied with an incomplete house and the builder's assurance that he tried his best.