Surely, it all depends if you have a charterable Hawker (or whatever aircraft you need) close to you airport of origin. You are obviously paying any positioning/depositioning costs to a charter operator, depending on where the aircraft is before your flight.
That's all well and good when you want to fly from an airport where an available Hawker is based, but not if you flight route is more obscure.
As I understand the Netjets policy, it's a standard hourly charge wherever your flight is from - on a certain aircraft size. Am I correct?