Hmm, does seem alot of money, so i went through a few web sites and got a price of all the parts needed to do it yourself;
Tyres, chainring, pads, chain, cassette, bottom bracket, bartape, cables, cadence sensor..... £247
Obviously the rim and rebuild you couldn't do, or the front wheel bearing, so if that gets added... £ 89
That makes £336 plus labour to fit bearings, so say £350.
So if you got all the stuff yourself and did all the work yourself (except wheel and bearing), you would have saved £215, but as you say, you've got peace of mind and you didn't have to get your hands dirty
I just found a forum where they are discussing how poor the chainring life is of the shimano chainsets, some guy said they were made of grey cheese, and im beginning to believe him , just checked my Dura ace outer chainring and most of the teeth are hooked. My chain had always been well lubricated and had stretched quite a bit less than a 16th of an inch, well within the limits. The sprocket teeth seem perfectly ok tho . Has anyone else got the same problem, best go and check
Steve