Another thing to consider in the question of weight of a bicycle wheel is the distribution of the weight and the effect it has on its rotational inertia. A wheel with fewer spokes and deeper rim profile (typically necessary to handle having fewer spokes) will be more efficient in terms of aerodynamics, but will be more difficult for the rider to accelerate. Losing a few grams at the outside of a wheel can make a huge difference in how a bicycle feels even to a non-professional.
Finer spokes have been done to varying degrees over the years, but are limited by material and the need for adjusting tension during the building process and ongoing maintenance. Spokes need strength most at the mounting points (traditionally a threaded nipple and J-bend). Also depending on the adjustment method (threaded nipple, etc...) a spoke must resist that twisting motion or have provisions to allow it to be held stationary while the nipple is adjusted. Double or even triple butted spokes are an attempt to concentrate material where it is needed the most, but at a higher cost of manufacture and less durability due to susceptibility to material flaws and excess work hardening in some cases.
Also, I am kind of fuzzy on this, but I seem to recall either Shimano or Zipp stating that the tipping point for number of round spokes to have an aerodynamics effect was 16 or 12. Any number above that did not have any significant difference in changing aero effects. Regardless it was a pretty low number.
Long story short, wheel/rim/spoke combinations can make a huge difference in the feel, durability and price of your bicycling experience and due to the huge variability in riding style and preference, no one combination is the perfect answer for all riders in all situations.