Nuclear electricity would be more than twice as expensive as gas for the simple reason that constructing a nuclear reactor is extremely costly, both in absolute terms and on a per unit cost basis. Electricity from gas would continue to be cheaper even if a relatively high carbon cost — even above $150/ton CO2 in some scenarios — were imposed. This large cost difference also negates the argument about the foregone opportunity cost from Middle Eastern countries consuming natural gas resources instead of exporting them. In reality, when the costs of liquefying and shipping these resources are taken into account, a country like Saudi Arabia would have to be assured that natural gas prices will rise to and stay well above the current and historical global average for decades, before it becomes a sound economical choice for it (and other natural gas-producing countries) to replace a natural gas plant with a nuclear reactor. The downward pressure caused by US shale gas expansion makes it unlikely that natural gas prices will reach the high levels needed to make nuclear power economical anytime soon.