Redknapp, whose only acquisition of the summer has been Brad Friedel on a free, said that the wage demands of top players are getting out of hand.
"You're looking to be a top-four team and it's difficult. We can't pay the wages that those clubs pay basically," he said.
"I think the wages have gone crazy. That is the problem. It's gone beyond all belief in the last little spell. We're well set up for financial fair play but it doesn't help when you look at what you're up against."
Redknapp also said that he hopes to "bring one or two more players in", which could include Valencia winger Juan Mata, for whom Spurs bid £22m on Friday.