It gets down to what you pay for your turbine aircraft , when the Porters were declared surplus from the Australian Army in the early 1990's they were going for about A$250,000 to A$300,000 by the time they were on the register and they were flying about 300 to 400 hrs a year.
It's hard to find any Porter or Caravan now for less than US$750,000-US$1 mil so it needs to be worked at Radars 500+ hrs a year to pay it's way.
We'll have a Skyvan coming up for about US$500,000 in 2010.
Indonesian built Casa 212-100s are cheap as they don't have FAA approval and are now 32 yrs old , probably in the range of what times are remaining on the engines and props (TPE331-5) , I reckon US$200,000 to $250,000 will get you one. The Indo Casa 212s would have to be on restricted reg in Oz , we had a quote for getting CASA type approval from a design office at about $300,000 which is a bit pricey for just one aircraft but if a bunch of them came in (5 to 10) it would make sense.
Kinloch , where are you based ? I may have a North Qld buyer for the Skyvan and if you're close by perhaps he can operate for you on weekends.