ManU bought their spine, though. Schmeichel, Cantona, Keane etc. were crucial in the 90's and later they bought players like Ferdinand, Rooney and van Persie to bring them trophies. Arsenal. And what would Arsene's early teams have been without Bergkamp, Henry and Viera? They all cost some serious money at the time.
So you don't need City like money but you do need enough to add quality to your side. Moyes managed to build good teams but his teams always lacked that little extra. Had he had money to buy three or four quality players who knows what might have happened. But the club could never afford the 50+ million.