6. Peter Schmeichel – Brondby to Manchester United – £505,000
The Dane was still a virtual unknown in the UK when Sir Alex paid a little over half a million for his services in 1991. He quickly established himself as the Premier League’s best and most fearsome shot stopper, forming a part of the United side that dominated the English football landscape in the 90s. Later went on to feature shortly for both Aston Villa and Manchester City, but there is still a strong case to suggest that United never truly replaced him.