Quote I got a month ago from my audi dealer was £170 for the key, and then roughly the same again for the labour.
I recently got a spare key from an independent key specialist - Car Key Solutions in London. It's not an official Audi key I think, but looks and feels identical - that was £165 all in, including coming out to you to do the work.
I had a couple of issues with that, the remote buttons stopped working, but the Car Key Solutions customer service was top notch and they sorted it for me.