Federal Prevailing Wage (Davis-Bacon) and Union Influence

I've commented on this before, but with so many current issues revolving around what public employees make vs. what private sector employees earn, the federal budget, and what your elected representatives are doing to change or not change it I think it bears revisiting.

Now this isn't about public employees. This is about private sector employees working on federally funded construction and other projects. All such projects fall under the Davis-Bacon Act which stipulates a "prevailing wage". This is the minimum an employer can pay their tradespeople while working on these projects.

"Prevailing Wage" is supposed to be representative of the average wage a tradesperson makes in a specific trade, but in reality is much closer to a union wage agreement between the government and the unions.

Because I'm most familiar with the painting industry I'll use this class of tradesperson as an example since I have knowledge of the true "prevailing wage" paid to private sector painters working on private sector contracts. I'm going to be conservative with the numbers, meaning I'm hitting high for their wages.

Private Sector Painter working on Private Sector non-union related work:
Hourly rate: $20.00 per hour ($41,600 per year).
Fringe benefits: $0-5.00 per hour ($0-6,000 per year).
Total: $41,600.00 - $47,600 per year (most painters receive near zero fringe benefits)

Private Sector Painter (union or non-union) working on Federally funded work (California San Mateo, Santa Clara, Santa Cruz rate) Source
Hourly rate: $34.50 per hour ($71,760 per year).
Fringe benefits: $16.87 per hour ($35,089.60 per year)
Total: $106,849.60

I highly value the skill and work ethic of the painters I work with on a daily basis and certainly would love to see them rewarded with higher earnings, but that is not the competitive rate seen in the open market for their trade.

So the question remains is why is the government (and there are similar laws in the States as well) paying double the true prevailing rate for projects? Simply to reward their union puppet masters? Speculation on reasons why the government supports this double standard is wide open with little forthcoming answers.

With so much rhetoric being sent around about underpaid teachers and other government workers I'd like to have either our elected individuals or either of the supporting major political parties (Republican or Democrat) explain their reasoning or justification for using taxpayer money (current or borrowed future) to spend in such a wasteful manner.