How they came about the money they earned is another story but if you're going to correlate title success with the amount a team spends, then you may need to underplay Fergie a little. For a long time they were the biggest club in England with spending power that dwarfed their rivals.
When Chelsea arrived they spent more money. In his last season he spent a lot of money on our captain as well. If we're going to put an empathisis on spending power at least remember Fergie was at the helm of one of the richest clubs in the world for a very long time.