As an L3 pilot, totally agree that you won't be able to carry that load and full fuel. But you can get a nice L3 for $700K, so I think it makes sense to double check that there's no way to carry (much) less fuel. Otherwise the L4 is probably the way to go... But you won't find a nice one for the budget you're talking about.
Since he has a 206 he already knows about the TT straps...
He could buy 2 R44s, and use a second pilot. You could do that for $800K, carry himself and six passengers and full fuel! Just saying! Turbine for 50 hours a year eats you up on the fixed costs... With the occasional expensive annual, you can easily hit $2,500 per hour @ 50 hours per year in an L3... More in an L4...
Does he do the full passenger & fuel thing all the time,. Or is that an occasional thing? Because sizing for that mission, and 50 hours a year is going to kill him on fixed costs... If it's an occasional thing maybe it makes sense to lease a 407 and pilot ( with the duals installed ) when he has that mission come up?