Oil changes every 3000 miles, or at least I will (only just bought mine) and if you can't or won't do it yourself then it's going to cost a fair bit. You never buy the cheap parts like you do with normal shitty cars, everything has to be at least very good if not top of the range if you want to get the best out of the supra and keep it running well.
Tyres, I've been told are almost £200 per corner :/ depending on how high a standard you are willing to go. They are ZR speed rated so not cheap.
Servicing if you don't do it yourself will cost you loads, you should only be getting the best parts for the car.
Of course you can get cheaper parts and I'm sure people will and swear by how they are just as good. But would you rather not be sure of quality? You buy cheap, you get cheap.
Over all it's the fuel to be honest. I've gotten through almost £100 a week since having it. But that's because I have no other car and I'm currently at home on leave from work, so I get bored easily and want to have a drive in my shiny new toy