With a lot of 50mm carbon deep v options popping up (November, Boyd, Williams) for around $1000, how much better is something like a Zipp 404 or Bontrager Aeolus 5.
Are these wheels worth double the cost of their less aero competitors?
I have both currently and can tell you that there is a minor difference, whether or not it is worth the money is up to you. In my opinion, it is not. Unless of course that minor difference will make you money or fulfill you in some other way. I have actually found that while my Zipps are slightly faster once up to speed my Reynolds DV46c UL's accelerate so much faster I prefer the Reynolds. On top of that the Zipps have been noisy, don't maintain spoke tension as well and flex more.
In the end, there are better ways to spend an extra $1500 or so.