This has been done over and over again here, and a quick search will reveal a lot of opinions on this topic. But, IMHO, there are three different issues wrapped up in the same issue of aircraft ownership;
Capital outlay in buying an aircraft
Fixed running costs (parking, fuel, scheduled maintenance, insurance, periodic renewals of paint, interior, avionics and engine)
Contingency funds
If you do a search of this forum, you'll find any number of threads running on the subject of the annual costs of maintaining an aircraft, cost of depreciation, the trade-offs made between owning say a new Piper Arrow and a 30 year old Piper warrior, and LAA aircraft on an LAA permit to fly verses an IFR equipped old technology spam-can on a C of A. Suffice to say that with say, a Piper PA28 flown for 200 hrs P/A based at an airfield around the M25 you can reckon on the following rough figures FOR RUNNING AN AIRCRAFT UNDER EASA IN THE UK (any minute now, someone will pop up and tell you what the running costs are for an aircraft in California...);
Parking £2,000 p/a
Fuel (32 lph @ £1.80pl = £68 x 200) £11,525 p/a
Annual + 2x50hr & 1x150hr check £3,000 p/a
Engine fund (£7.50 p/h x 200) £1,500 p/a
Insurance £1,400 p/a
Total for the year £17,950 p/a
Cost per hour £88.1 p/h
On top of that you will have to have a contingency fund; that is to say that in aviaition, when things go wrong, they tend to be expensive. Even though that 500 hr engine has run like a swiss watch, it may start making metal tomorrow, and need replacing. Your annual inspection might reveal spar corrosion, which will necessitate a replacement wing. A factory A/D may result in all your seatbelts being replaced.
Similarly, we seem to be living in troubled times vis-a-vis legislation. If suddenly an item be comes mandated (like we were all told Mode-s was about to be mandated) you will have to dig into your pocket. If 100LL gets replaced by something different, you may have to overhaul your engine in order to allow it to run on fuel without tetra-ethyl lead. You need to have the ability to write a cheque for £20,000; sod's law says that if you have that ability, the chances are your bluff won't get called - if you don't, it will invariably be the next call you get!
Having said all of that, if you don't actually need that Rockwell/Piper/Cessna/Beechcraft spam-can, and will consider a new generation LAA 2 seater, the picture is entirely different.
Rod will be along in a minute with the figures....!