You must be new to United's finances under the Glazers. It's looking more like Pogba was a one time thing.
I think you're new to United's finances, they spent the same and more from some of the previous managers compared to City. The problem is that majority of your managers just plain sucked in which players they targeted.
Fred - 59 million (looks quite awful)
Lukaku - 84.7 million
Matic - 44.7 million
Lindelof - 35 million (not consistent enough)
Pogba - 105 million (looks disinterested)
Mkhitaryan - 42 million (traded for Sanchez)
Bailly - 38 million (not consistent enough)
Martial - 60 million (looks disinterested)
Schneiderlin - 35 million (sold at 22.9 million)
Depay - 34 million (sold at 16 million)
Darmian - 18 million (not consistent enough)
Di Maria - 75 million (sold at 63 million)
Shaw - 37.5 million (injury problems)
Herrera - 36 million
Rojo - 20 million (not consistent enough)
Blind - 17.5 million (sold at 16 million)
I am not a fan of all the players Arsenal have bought lately, but if they had this type of level for spending we would be a title contender.
Robertson is better than Mendy.
Lol, he has the potential to be better, but definitely not currently at any part of the pitch.