Signing on fees

I recently read Roy Keane's Autobiography for the second time (would recommend it to anyone). What stood out for me is when Roy signed for Manchester United in 1994 was he asked for £250,000 a year but a signing on fee of £500,000. This 17 years ago and Roy was signed for £3.75 million a British transfer record. I just don't think people realise that even with wages and transfer fees there is still a lot of money to pay to sign a player.