That's going off the assumption that the more money spent on players, the more successful you'll be and that the more expensive the player, the better he is. In theory this is true whereas in practice it doesn't always work like that.
SAF has only bought 4 players over £20m, Rooney, Berbatov, Veron and Ferdinand and he's also funded a lot of his purchases with sales (Beckham, Veron, Heinze, Smith, Richardson, Rossi etc etc). It's not about how many expensive players you have, it's about assembling a good squad and buying the right players. You could argue that both manager's most expensive signings have been hit and miss (Veron and Berba for Fergie, Keane and to some extent Johnson and Aquilani for Rafa). The difference between a £3m player and a £15m player isn't much, most of the cost comes from a media hyped reputation and the standard of club the player is currently at, the difference in actual skill is not that great and the mentality and psychology of the player is more important.
Everyone says Berbatov is a £30m striker so he should score more goals. This is flawed, he was only £30m because SAF was desperate for him and Spurs did us by stringing us along all summer until deadline day then getting us in a bidding war with City. This puts increased pressure on him as realistically he's a £15-20m player, and while his contribution is good (better than most 2nd choice strikers and almost identical to Tevez's record this season), he now feels he has to do more. Wenger has shown that you don't need to spend a lot of money on players for them to be good and to build a decent side and the fact they've had a considerably better season than you is testament to that.
Like Beboq said, Rafa has got the club by the balls, he negotiated that contract (the longest in the league) knowing he had the backing of the fans and the security to do what he wanted due to the financial implications if he was sacked.
Truth is he's performed poorly at times in the transfer market and his dealing with players already at the club and this has hindered any progression. It's too easy blaming the owners for all the problems, they've sorted an £80m shirt sponsorship deal with Standard Chartered, a £150m deal with adidas is close to completed I think, they paid a shit load in unnecessarily high signing on fees to the likes of Torres etc when renewing their contracts (which came out of the transfer budget and Rafa was aware of this) so they've really not been that bad. Yeah they bought the club with loans but they've had little bearing on the on-field performance, this comes down to the manager and the players and I believe it's the attitude and psychology that's the problem.
Anyway, they're off now so you all got what you wanted, now it's time for Rafa to prove me wrong and prove you lot right with no pesky Yank leeches to hold him back.
