Bale, they paid an intial 5 million rising to 10 million. Although I think Southampton accepted an early fee.
We simply don't have the luxury of spending 5 million on a player that won't contribute for another 3 years. He was awful in his first two seasons and only started playing well in his third. If we pay that much we need someone who can contribute immediately.
I should also point out that you are using one player as an example which doesn't necessarily represent the rule.
For every Gareth Bale that is bought for decent money at 17 or 18, there are 4 or 5 others that never repay their fee.
Even a team like Spurs, that has generally bought very well, have a huge number of duds.
Look at Kyle Naughton, only this year is he getting any time on the pitch and it's not much. They paid 6 million for him.
Other shit transfers:
David Bentley 17 million
Bassong 8 million
Alan Hutton 9 million
Dos Santos 4 million
And a litany of players we've never heard of for between 2 and 4 million because they never made it.