Ever since I qualified as a ski instructor, I've had a pair of Oakley sunglasses (it's sort of ski instructor law). They're by far the best glasses I've ever owned - somehow Oakley seem to make their lenses just the right darkness and colour to work well in the sun and the shade (and in my case, on the Tube too ;-).
A couple of weeks back, I managed to scratch the right lens really badly. It was pretty terminal, so I decided to contact Oakley to see what they could do. They couldn't give me any indication of cost until they saw the glasses, which was a shame. However, about a week after sending in my glasses, someone called me to say it would be £49.99 to change the lenses.
I've just received my glasses back. Not only do they have new lenses (the old ones got returned to me too), but also they've got new rubbery bits on the ears (which Oakley call Earsocks or some such), new nose pads, the screws are all tightened up and they've been bent back into shape. In short, they're pretty much new all over again.
Oakley: Not cheap, but you can't fault 'em.