Transfer: Sydney FC to Sheffield United, 2007
Price: $125k
Impact: Carney has quickly become a fan favourite at Sheffield United, making stand-out performances in the League Cup and FA Cup, as well as scoring important goals for his side in the Championship.
Money well spent? This one looks like a doozey. Sheffield United have reportedly already rejected a £2.3 million bid from Anderlecht amid interest from several large continental European clubs. No doubt about it, Sydney FC were fleeced!

Transfer: Millwall to Blackburn, 2001
Price: £600k
Impact: Blackburn got a bargain when they signed Neill, a moderately promising lower league utility defender. In more than five years at Blackburn he became captain and was one of the side’s most consistent performers as the unfashionable side perennially overachieved.
Money well spent? Though Blackburn fans won’t forgive Neill for joining West Ham in 2007, they still got several times what they paid for Neill even though his contract lasted just six more months. More importantly, £600k for a quality Premiership performer is a sensational steal.

Transfer: Croatia Zagreb to Celtic, 1998
Price: £3.5 million
Impact: Although a stressed Viduka almost quit the club soon after he signed, he went onto become a success at Celtic, scoring 27 goals in his only full season at the club and being named Scottish Player of the year.
Money well spent? Though Celtic were beaten by Rangers to the title twice in Viduka’s time there, the player was one of the club’s star performers. Celtic also made a profit when Viduka left for Leeds in 2000 for a transfer fee of £6 million.