Manchester United chief executive David Gill has poured scorn on Manchester City and Real Madrid's huge spending in the transfer market this summer.
United have lost Cristiano Ronaldo to Real and Carlos Tevez to City, but Gill has questioned the long-term wisdom of throwing around such vast sums of money.
He told reporters: "It is highly unlikely that we would want to go to those levels. We don't think it's necessary because we are looking to the medium and long term.
"United has been around since 1878 and our job is to make sure it is still around for many more years in a sensible fashion.
"That is by generating our own income. There will be ups and downs but, overall, we think that what we are doing is having a sustainable business model for the long-term.
"I don't understand the economics of what Real Madrid are doing.
"Their turnover is not materially different to ours, so I am not quite sure how they can make the profits to justify the salaries.
"It's none of my business I suppose, but I don't think they can."