sorry, I have been looking at the cs206 and I can get a usefull payload of 500kg. so because the flights are so short, i could potentially do 2 per day.
and looking at the poly box dimensions, I can get approx 400kg or 20 boxes into the cabin, if I remove the back seats.
Looking at prices, I have seen a 206 on floats for 190-260k usd. they are old.