Reality alert: The top4 don't bring their own youngsters through so they have to spend more. Even Arsenal buy their 'youngsters' for hefty sums from other clubs. I think people underestimate just how much is saved in transfer fees and wages when you can bring just 1 or 2 youngsters through each season, even if some seasons they are only squad level players they still save a lot of money.
To keep hold of the youngsters, it's still necessary to pay em. Like a few others on this thread, you're confusing transfer fees with wages. It's the wage bill that tends to cripple clubs that overeach themselves.