We've been buying success for years. Look at the title winning squad from Fergie's final season. It's almost entirely based on players who were bought. RVP was our big signing. Rooney was bought as a youngster. Carrick was key that season; he was bought. Rio and Vidic? Yep, you guessed it. DDG? Bought. Our only homegrown players in that team were really the ageing Giggs and Scholes, along with Welbeck and the rather useless Cleverley.
Yeah, City and Chelsea have bought success; in that they spend money on trying to improve their squad, like we do. I'd like to think that one of Fergie's greatest qualities was being able to find magnificent players for small amount of money: Schmeichel, Cantona, Vidic, Evra, VDS etc, but he still bought most of his players, especially in later years when we failed to produce any top class youngsters.
The idea that they're somehow 'hollow' is only really an opinion, and one that the vast majority of their fans probably struggle to particularly care about when we're sitting down in 5th.