I destroyed a wing mirror on a Golf a few years back. Admittedly my 'weapon' of choice was 1.3 tonnes of car, but the destruction was impressive given I only hit it with the wing mirror of my car, which survived with barely a scratch. (In my defence I was driving down a road narrowed by parked cars on both sides and a Transit decided it could fit coming the other way. I'm a pretty good judge of such things and decided otherwise, so I had to choose between skimming the mirror or hitting a Transit)
Anyway, two things:
1) I'm glad wing mirrors are designed to shatter on impact. I'd rather be hit by something that breaks than something that doesn't
2) It took me some time to get back to the Golf as I had to park down the road and walked back. The owner was so pleased that I came back (he gets through a lot of wing mirrors, he said) that he said he'd take his car to the cheap place he'd found for wing mirrors rather than the VW dealer. I didn't claim on my insurance as it didn't seem worth it for the loss of no claims and £50 excess, so it cost me £250 - but that was 10 years ago. £280 isn't bad. Don't forget that you get someone to fit it for that too.
Oh, and 3 - I should get insurance. I crashed in to a taxi when I was a kid and the bonnet repairs cost £150 (in 1990) - I got in to a fair bit of trouble for that