I've TRIED to give my money away on sunglasses, I went out with a £100 budget and still couldn't find anything.
My favourite sunglasses I spent about £8 ($16?) in Dorothy Perkins 2 years ago and I've had about 10 pairs of them and I have one pair left.
I ADORE them and luckily they keep bringing them back every year. I leave them in shops, on buses, at friend's houses, I drop them, scratch them... etc. Maybe I shouldn't spend $200 on a pair!!