At an OPC I think the prices you mention are pretty much correct.
Turbo servicing is not so different to the C2. I can look in the service book later to see what the items are. I think spark plugs are changed more often and there are a few more things to check (adding an hour or two to the service) and it has an extra litre or two of oil.
Tyres are the same as on the C4S.
If everything goes well it is not so bad. The issue comes when things start wearing out or breaking.
Front driveshafts, front diff, transmission shaft, is the same as the C4, so should not be too different in terms of price.
The brakes are the same as those used on the 997 C2S, so prices should not be too much of a rip off.
I wouldn't think the turbos cost too much, and the intercoolers should not fail.
The two expensive items are the gearbox and the engine.
The would guess a new box would be 5K or more (I don't really know), but you shouldn't to replace it often.
The engine is lots, I'm pretty sure it is in 5 figures if you wanted to replace the whole thing. Whilst it is reliable, it is a big chunk to find if something did go wrong in a big way.
I would opt for the warranty, just for peace of mind.
