Cahill, at £1.5m one of David Moyes' best bargains, thinks spending fortunes could actually shatter that.
The Aussie, 31, insisted: "Loyalty is very important at any club when the chairman and manager want you to be part of the revolution.
"We share that vision and I think we're up there in terms of what players can achieve. We don't have the funds to spend a lot but that's the clever part of what the manager does.
"He always knows what he's getting and the question with new players is what suits the team. You could probably put Fernando Torres up front for us and would it be right for us? Maybe not.
"If you give a manager £20m to buy a striker or a winger, will it be any better than what he already has and is it going to help the team?
"We have never spent money like that - spending money does not always work out. For the seven years I've been here, it's been nothing but unbelievable."