Wind farms, as with solar farms and nuclear energy, have large up-front fixed costs and negligible marginal production costs. If the wind-farm produced _only_ 1 hours worth of energy, then $3.00 per watt would be spot on, as I understand it.

Likely the wind-farm will operate a number of years. Let's suppose it produces at 10% capacity for 20 years. That would be equivalent to 100% capacity for 2 years, which would be 50 MW/h * 24 hour/days * 365 days/year * 2 years = 876,000 MW/h

So now you have $50 Mill/ 876,000 = $57.08 per MW/h, or $5.7088*10^-5 cents per watt/hour.

Now, suppose the capacity is larger or the time lasts longer. The cents continue to fall per watt/hour

You say that as though it's a lot. And it sort of is a lot for an initial investment. But the cost of keeping a wind farm running is a lot lower than the cost of keeping fuel consuming power plants running. This wikipedia page has a bunch of estimates of overall cost per Megawatt Hour that show wind being a slightly cheaper source of energy than conventional coal plants, and considerably cheaper than more advanced coal plants.

http://en.wikipedia.org/wiki/Cost_of_electricity_by_source