Wish this was on the PS5...
Me too. If the sales aren't high enough, Microsoft may reconsider and decide to sell it on the PS5 (probably with some DLC included) a year later or so. It cost them a whole lot of money to buy all those companies, including Bethesda, and they're going to eventually have to recoup a profit from those purchases.
If that means releasing on Playstation again, I think they'll do it rather than risk losing money. Even Disney has learned with Disney+ that having your own exclusive platform and not sharing isn't great business sense. It costs them a lot of money every month to host everything and produce content, and if they don't license out that content to competitors, they can't make their money back.
I can see Microsoft learning the same lesson. Especially given that Disney+ hasn't been profitable ever, and now the red ink is starting to catch up with Disney. If keeping big games from big studios starts losing Microsoft a lot of money, I think they'll fold, at least partially.
So what is in the "PC" version that isn't in the Steam version to make that size disparity?
Different delivery method.
Gaming