The Spanish giants paid Manchester United a world record £80million for Cristiano Ronaldo last summer but teams don't always have to break the bank to land a superstar.
At the other end of the scale we have the free transfers.
Inthe week that Arsenal legend Sol Campbell rejoined the Gunners,Sportsmail's team of experts have come up with their favourite freebies.
And, as always, we want to know what you think about The List.
Read Nos 50-41 Read Nos 40-31 30 Paolo di Canio (West Ham to Charlton)
It was a push on referee Paul Alcock that ended the Italian's career with Sheffield Wednesday but West Ham fans didn't complain when he arrived at Upton Park in 1999.
However, the Hammers faithful were disappointed to see him leave for Charlton in 2003 after relegation to the Championship.
His season at The Valley wasn't littered with goals but he helped the Addicks to their highest top-flight finish since the 1970s - seventh - which must seem like an eternity ago now.
Never a dull moment: Di Canio
Midfield maestro: McAllister
29 Gary McAllister (Coventry to Liverpool)Questionable signings are a hot topic around Liverpool of late but just as Rafa Benitez's judgement certainly leaves plenty to be desired, his predecessor Gerard Houllier took some stick for signing 35-year-old McAllister in 2000.
But the move proved inspired as the club embarked on a trophy-winning spree with the former Leeds man firmly in the mix.
He loved a dead-ball situation and scored some memorable goals -, including that long free-kick against Everton - and helped the Reds to five trophies in 2001 - the FA Cup, UEFA Cup, League Cup and UEFA Super Cup, plus the Charity Shield.
28 Henrik Larsson (Celtic to Barcelona)Recently retired, the Swedish striker ended his career with plaudits from every club he played for after endearing himself to the players and fans of Helsingborg, Feyenoord, Celtic and Manchester United but it was his brief cameo at Barcelona that set him out as one of the finest free transfers.
Despite injuries, his goals helped Barca to two Spanish League titles - in 2005 and 2006 - a Spanish Super Cup and he was also instrumental in Arsenal's downfall in the Champions League final in Paris four years ago.
Swede dreams: Larsson
Top drawer: Vialli
27 Gianluca Vialli (Juventus to Chelsea)The first of three Italians to manage Chelsea, Vialli joined from Juventus to score goals but six months after the FA Cup victory in 1997, Ruud Gullit was sacked and the former Sampdoria striker took over.
Within four months of taking the reins, Vialli had won the League Cup and European Cup Winners' Cup and finished fourth in the Premier League. The following season he took the club to the quarter-finals of the Champions League.
Things took a slide from there but his tenure was regarded a success before the Russian revolution arrived on the Kings Road.
26 Jean-Alain Boumsong (Auxerre to Rangers)OK, I know what you're thinking, but there's no doubt that Boumsong's move to the SPL turned out to be a fine piece of business by Rangers boss Alex McLeish in 2004.
The centre-back played enough games to secure a Scottish Championship medal and boosted the Ibrox coffers by an incredible £8m after his move to Newcastle.
A great bit of business by McLeish - not such a great move for Boumsong or the Magpies.
Big hit: Boumsong at Rangers
Cherries on top: Anderton
25 Darren Anderton (Wolves to Bournemouth)Anderton somehow managed to stay injury-free long enough to enjoy an Indian Summer of sorts after he signed a pay-as-you-play contract with Bournemouth in 2006.
On his debut, without even the slightest hint of a niggle, knock or impending spell in the treatment room, former Tottenham star Anderton scored a spectacular 40-yard free-kick and in February the following year, he scored his first career hat-trick.
In all he managed 78 appearances for the Cherries and scored five goals, the last of which came in his final professional game.
It was, quite fittingly, his classy volley that won the match for the south coast club in the 88th minute.
24 Ruud Gullit (AC Milan to Chelsea)The former European and World Footballer of the Year played for some of the continent's biggest clubs but he still reveres his time with Chelsea as his happiest.
The two-time European Cup winner (with AC Milan) enjoyed a successful time at Stamford Bridge that ended with him managing the club.
A year after joining from Sampdoria he became player-manager and led Chelsea to their FA Cup victory in 1997.
Wembley winner: Gullit
City slicker: Dugarry
23 Christophe Dugarry (Marseille to Birmingham)At today's prices how much would a European Championship and World Cup-winning striker cost you? Somewhere in the region of £20m - but not if your name is Steve Bruce.
The Birmingham boss nabbed Dugarry for nothing in 2003 after he had impressed during a loan spell from Bordeaux which included a run of five goals in four games.
22 Antonio Cassano (Real Madrid to Sampdoria)As well known for his fiery temper as he is for his goals, Cassano has never been one to shun the limelight and a series of disagreements hastened his departure from Real Madrid.
He remains a controversial character since his move to Sampdoria where he is just as likely to be seen celebrating a goal as he is throwing his shirt in disgust at the referee (again) for yet another decision he disagrees with.
Passionate Italian: Cassano
Rolling back the years: Merson
21 Paul Merson (Aston Villa to Portsmouth)Merson's brand of creative football out on the wing made him a very useful player for a number of clubs after departing Arsenal but his finest hour post-Gunners came at Portsmouth.
Merson was a key figure in Pompey's return to the top flight in 2003.
He wasn't about goals - netting two in 45 appearances - but his understanding of the game and willingness to help his less-experienced team-mates really made him stick out.
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