I bought a 32 GTR in March, and since then i have spent just under $10k getting it safe for track days etc, and i still have at least another $5K before its bulletproof, and then i need to budget for the gearbox blowing up (fingers crossed it doesn't), and possibly another engine rebuild (hopefully not for a few years as its just had one), along with a few cosmetic things such as dings getting pulled out and a respray, maybe gut the interior and put a cage in blah blah blah.
Note that these aren't costs incurred by owning the car. It is simply my hobby and passion to modify the car the way i want it and drive it accordingly. the running costs i think are fairly negligible, not much more than most other 6 cylinder cars.
At the end of the day, you need to sit down and really think about what you want out of this car, look at the price of the car, and then say to yourself "how much do i really want to spend here", because the listing price is only half of the story. The faster you want to go, the more expensive it will be end of story.