The cost of charge depends on several variables: The top three contributors are (1) the charging cost at the particular charging station. (In my area at a public charger it runs $.50 per Kwh); (2) the capacity of the battery in kilowatts, and (3) the duration of .the charge.
A full charge--depending on battery capacity--can run $8 - $10, and that's for a BIG battery (think Tesla).