Factoring in the cost of decay as part of the overall expenditure I'd say 90-110% return almost all the time (not including the anomalous hunts where you get several globals or a hof etc). I can honestly only remember having one truly awful hunt but I can't even remember what it was on...
Saying that, the average return is much lower if I do wreckless hunts on mobs that need too much fapping etc but I expect that before I start. I didn't count them among the overall average because for me those wreckless hunts are things I do every now and again to let off steam and don't expect much return.