I hear if you have Amazon Prime and pre-ordered FO4 on Amazon, it's coming to less than $35 before sales tax on both consoles:
http://i.imgur.com/jjzwdkS.png
That must have been an error that has since been fixed. I just added the Xbox One version and went to checkout and the Prime Discount is only showing once. That brings the total down to $49.99 which I would take since I have a lot of Amazon Store credit on my account from winning my fantasy baseball league right now.
Unfortunately the Prime credit doesn't seem to apply to the PC retail or download versions. It's console only for some reason. I want the PC version for full mod support and better performance.
Edit: Just checked the PS4 version and it's showing the same as Xbox One price.