Basically in spite of the debt that the club is footing repayments for, the club's revenue streams are still extremely strong - the strongest in the world if you discount #2 Barcelona who relied on a weak Sterling exchange rate to pip United back to third, and #1 Real Madrid who, in essence, enjoy state funding. They post sizable profits each quarter even after debt repayment, and their debt is shrinking considerably (
link). They could afford a sizable transfer fee if it was seen to be 'worthwhile' and in the club's long-term interests, although yes, their ability to buy and pay whatever they want at a drop of a hat is considerably diminished since the takeover.
Ultimately letting the club stagnate is not option for the Glazers, even seeing it as a business it is not in their interests either to plough everything into debt servicing - people seem to forget they need trophies in the cabinet and stars on the pitch for their financial strategy of increasing their profits in markets like Asia and the US to even have a hope of suceeding. The droves of City fans coming out of the woodwork, and Chelsea fans before them, show that no-one likes to support losers. The pressure being mounted on them by rival groups for yet another takeover, even mentioned in that article, adds yet more pressure for them not to be seen to be 'holding the team back'.
In essence what Fergie and Gill are saying is not contradictory, Manchester United has the ability to shift its weight about in the transfer market (and then some), it's just that while Chelsea can afford to blow tens of millions on 'maybes' like Shevshenko and co., it would be more costly to United if not anything near a 'deathblow'. Softly does it for now.