Its a fairly easy argument to defend manu's spending vs chelsea. You just have to take a larger timescale, something runeedge's post didnt seem to contain.
Firstly they have generated a huge amount of money through succes (a balance of good buys and a great youth team) and good marketing, chelsea on the other hand "won" the title after going so far into debt that they needed to sell the club and managed to attract a billionair. Who subsequently financed a whole new team being bought. Which then "won" the league. There's a big difference. One has succes through history, good management and good football, the other by being in debt and ending up a plaything.
However, manu's spending this summer is very excessive. Although theyve only bought one player that will likely be a regular (hargreaves) the rest are youth or backup (kuszciak). And if the tevez thing goes ahead they will have bought 2 first team players. Still not a lot really, just huge sums being spent.
If liverpool spend another 30mil on 2 wingers they will have signed 3 first team players, more then manu from that perspective. But then its needed