Basic numbers

Gasoline provides about 130 MJ/gal.

A kWh is 3.6MJ so the energy in a gallon of gasoline is about 40 kWh.

Given the inefficiencies of the chemical processes needed to make liquid fuels from water and air, and the need to pay for huge plants, dollar a gallon synthetic gasoline implies a penny (or less) per kWh electrical input.

So if dollar a gallon gasoline is the goal, penny or sub penny per kWh electric power is a way to get there.