Interesting. Don't really care what fee we sign him for, if United decide they can afford it they can. They're also not stupid enough to seriously hamper any future spending in the next transfer window or two by blowing it all on one player either.
Comercially, Pogba will make a chunk of it back, through sponsors, merchandise etc and if he helps us back into the CL he'll pay off a big chunk of that fee again. Lastly, he's of an age that if we decide to sell him on in a couple of years, we'd probably break even on him at least.
Playing wise & the Rooney question - I wouldn't be suprised to see.Rooney up his game quite significantly in a team with better players around him. He has been largely slow and awkward over the last 18 months, but with the new players around him I think a bit of the pressure will be off. And is he doesn't perform, Mou will have no issue dropping him either.
Ultimately, in Utd's current position, worth the gamble.