it has a theoritical low overall cost because the situation only occurs 36 times out of 10,000 hands. So looking at the total wagered every 10,000 hands, what you do to save a fraction of a bet 36 times is pretty meaningless. There is no variance reduction because you are talking about .5 of a bet difference 36/10,000ths of a time.
Using this logic, in a multideck shoe if you are dealt two Jack of Spades and the dealer is also showing a black card (it doesn't matter which one), You should HIT your 20. Over 10,000 hands the additional amount you lose hitting this 20 instead of standing is even less than what you lose by taking even money.
So hitting 20 vs a black card (when the 20 is two jack of spades) is better than taking even money.