Hate to be the one to say this but City' defense signings hasn't cost more than 50m per player. They got rid of all their fullbacks after Pep's first season and replaced them. They then went out and brought in one o the best young defenders in La liga(Laporte) While bringing in Stones. Say what you want, they have 4 quality CB to choose from along with good fullback options. Though they are a bit weak on the left fullback position.
The question you have to ask yourself is, City's record signing is Mahrez at around 60m why is it that United is constantly over spending on players when their rival is spending just as much but is getting more quality. City will spend 200m and bring in 4 players united would spend 200m and bring in 2 players.
Laporte cost city 50m, Maguire costing you guys 80m. laporte is the better purchase. Better value for money.
That's what's been holding united back, the value per pound is not there.