To be fair, that's all United's been trying to do, buy prestige with the Ronaldos, de Beeks, Sanchos, Varanes, Sanchezes... and it's not quite worked out post Ferguson (who was really lucky to do it with a final prestige buy in van Persie). City's got a lot of money too but they've kept buying just below prestige level and worked to build them up.
Also, you can't really force a marriage for transfer policy with club playing style (IMO). If United want to modernise their transfer policy, then they have to modernise their playing identity first too. Ferguson built a club that relied on the van Persies, Ronaldos, Rooneys, Cantonas, to do the job for them at the front. They have to dismantle that first.