Originally Posted by jrobe

From this chart, you could conclude about a 10 watt advantage at 30 mph going from a 20mm rim to a 60mm rim. I would guess that the advantage under 20 mph would be under half of this (or < 5 watts).

The original poster states that he does primarily solo training rides (and frequently gets dropped on group rides). I don't know what his typical riding speed is but I bet it is under 20 mph. In other words, he has to spend megabucks to gain about a 3-5 watt advantage.

He would in all liklihood, benefit far greater from a better training system (maybe a power based system) than from very expensive wheels.