In order to get a mode that was a free update to FO4 you need to shell out at least $15 to get the intentionally dickishly priced Survival Mode for Skyrim. The 800 "credit" price point was not an accident, they couldn't have accidentally made it just 50 points above what the cheapest pack of microtransaction motherfuckery gets you. So you are going to have to fork over 1/4 of the original price of the game to get what was a free update in FO4. They put the two Doom items for FO4 (Armor and BFG) at the same price point and for the very same reason.
So Fuckthesda is committing suicide and I'll be glad to see them die honestly.