I think Target isn't the right comparison here - the skills required for this project are worth much more than minimum wage bagging groceries. If you assume something like $50 an hour (on the low end for a skilled electrician), you get to the $6800 number in the parent post pretty quickly.

Getting certified and hired as a skilled electrician is a lot more complicated and much harder than acquiring the knowledge to be a skilled electrician. There are many people working Target-level jobs with that level of skill in some area.

That number was from 2016 is useful in determining if it was worth it but not useful if it will be worth it staring today as the number has changed in the intervening 9 years. The number will keep changing with an estimate of $80 kWh by 2030.