Purchasing, maintenance, flying costs, etc.
All depends on what "Private Jet" you own. Lets start with a Gulfstream G550 (which congress wants to buy several of) They start at 40mil US and range up to 70mil!
Now to run the thing there are both fixed and variable costs.
"Variable operating costs (Fuel, Maint, Trip expenses) are around $2,300.00 per hour while overall ownership expenses (including maintenance, storage, crew costs and insurance) could be around $600,000 per year.
This does not include costs for periodic maintenance procedures such as $1,000,000.00 for an engine rebuild, $ 200,000.00 for a paint job or $300,000.00 if you want your interior refitted." (This is from both Wikipedia and Gulfstream sites)
Now suppose you want a smaller jet like the Cessna Mustang VLJ the buy in is less as well as fuel etc. They start at 1.75Mil US and only around 1200/hr to operate.
Want an OLD Jet like a 1970′s Citation, you can find some good ones under 1mil in fact some around 300-500K (but be careful they may need an engine overhaul at about 250,000-300,000 and they have two of those! Expect to also repaint for around 70K-100K and renew the interior also around 60-90K and expect some other "repairs". )
They still use about the same fuel as new aircraft and cost more to maintain since they are older. Hangar rent and pilots expenses are still the same etc etc.
It is not inexpensive to own a private jet of any size.