This cost difference is known as a green premium.

这种成本差异称为绿色溢价。

But that cost explains only about 10-20% of the cost difference.

但这一成本仅能解释10-20%的成本差异。

They're more expensive than gas-powered cars, but the cost difference has been shrinking rapidly since 2010.

它们比汽油动力汽车更贵，但自 2010 年以来，成本差异一直在迅速缩小。

But current research efforts are also looking at doing just enough work by machine to close the cost difference between U.S. and foreign factories.

但目前的研究也着眼于用机器完成足够多的工作，以缩小美国工厂和外国工厂之间的成本差距。