Well, if you base the costs off of a traditional aircraft (around which this is based), they'll be in the $100+ an hour range, minimum. The cost to buy will be in the $2-300,000 range, minimum. They will require yearly maintenance, not counting any maintenance required on the electric props and batteries. This is based off a production aircraft, the Cirrus.

I'm also not immediately seeing how this would not require a pilots license - more likely a helicopter license, though this is easily debatable.

So perhaps not billionaires, but millionaires to be sure.