a nuclear power plant costs 6-8 billion up front, before you get a dime back and takes 2-8 years to build. Nobody in the US except the government will loan utilities the money to build or upgrade a nuclear power plant. I'm all for nuclear power, but it ain't cheap.
The electric generation system is actually a remarkably apt comparison because in most districts the cost of consumables is marginal. The real cost is in the capital expenditure needed for the system to supply a given load. Many of the same principals apply (e.g. "why do they charge me per kWh when they're overgenerating and they have all these nuclear power plants sitting around....")
