They shouldn't be in the same price range. It's more expensive than it should be - this is for all 10 series cards - due to them no longer being in production. The 2 cards are NOT in the same performance tier either. 2060 is the faster card, but your current cpu would hinder it.
So get either an overpriced 1060, or upgrade the cpu to 7700(bios update required beforehand), because your 6400 can't go toe-to-toe with the 2060.