Why on earth is a government-protected monopoly entitled to 10% margins?

Indeed, how do they pick any margin? If higher is better, why not pick 1000%? If lower is better, why not pick 0%? If we want something reasonable, why not make it market based to figure out what people think when they have to stump up real resources themselves? Once profit margins are set by committee decision there is little point trying to claim that the concern is profit motivated. The profits aren't doing much useful signalling. It just sounds stupid.