Inefficient energy efficiency

This paragraph jumped out at me in this morning’s paper:

In Nevada, lawmakers agreed that strings attached to the stimulus would require them to pay the prevailing union wage -- $46 to $57 an hour -- to construction workers who will fan out to make buildings more energy- efficient. Still under debate is whether the state should pay equally high wages to workers hired under a locally funded weatherization program, which typically pays $15 an hour.

I realize that the ruling coalition includes labor and environmentalists. I also realize that workers would rather be paid $50/hour rather than $15/hour.

But why would taxpayers want to pay 3x market prices for such work? If the government is trying to be efficient, why not leave it to local states to decide what the best use of funds are?