These extreme cateye sunglasses made their debut at Alexander Wang's spring 2010 show. The Alexander Wang for Linda Farrow shades retail at boutiques like Opening Ceremony and Oak for $325; though interesting to note, they're only $288 at lindafarrow.co.uk.
If $300+ is out of your price range, you might want to consider these vintage frames (below). I personally like them more than the Alexander Wang pair because they're slightly less severe, but still edgey.
You can find them for under $20 on eBay and at 80's Purple. On the eBay, the seller has 10 pairs of these "Vintage Cat Eye Deadstock Sunglasses Hot Bad Ass Shades" for $13.95 + $5 S&H. At 80's Purple they're slightly cheaper, $10 + $5 S&H, and available in brown.