Do you really think that it's of benefit to society for some people to show up to work every day and take home Wal-Mart wages, instead of having real alternatives?
A large share of this government waste goes to military contractors employed in completely unnecessary wars such as the multi-trillion-dollar mess in Iraq.
Also, please cite your "on average double" statistic. If my memory serves me, the discrepancy is about 30% on average, mainly because private-sector pay is far more recession-sensitive. (The discrepancy would shrink, if not reverse, in a growing economy with a healthy private sector.) For the record, low-level government employees do make more while upper-level people make considerably less than they do in the private sector.