When it comes to equipment, you're buying seconds. And they aren't cheap.

If you're going from a regular box-section rim to, say, a Zipp 808 wheel, your aero drag does get cut in half. Going from a Williams 58 tubular (i.e. the Zipp 404 rim shape from a couple years ago) to a 2009 404 is going to be much less.

It's important, though, to remember that these small advantages should never deter you from buying really cool bike **** if that's what makes you happy.

Now granted, part of this purchase I'll be making this summer is for comfort/function/adjustability, but it can be had much cheaper. These bars just kick ***. Sure it might save me 2-3 sec in my next olympic tri from aerodynamics alone, but the placebo/feeling like a badass effect is good for at least 10-20 watts.