When making any comparison, you can only compare apples with apples. Solar and wind are quite different from coal and gas and nuclear.
To get any reasonable comparison you would need to add the cost of full backup to solar and wind costs. Not just a little battery here or there. No one ever does that though!
Its a bit like saying I can buy a few minis instead of one semi trailer to transport my goods. The cost of those minis is far less than the cost of a semi but who in their right mind would try that comparison?
