Barcelona have been one of the giants of the game for a while. Their current financial struggles and management issues do not take anything away from their rich legacy and history.Letting Lionel Messi go was not what the Blaugrana would have wanted to done. However, that had to do so to avoid falling foul of the La Liga's stringent financial fair play rules.Barcelona hope to bounce back stronglyThe Spanish giants have signed some top-quality players over the years, and will continue to do so. At the same time, they have also sold a number of their key players.Much to their credit, Barcelona were able to make good profits off most of them. Without further ado, here's a look at the five most profitable sales the Blaugrana have had over the years:Note: All values are as per Transfermarkt,#5 Yaya Toure - £18.9 millionYaya Toure was one of the key players in the Blaugrana's 2008-09 treble win.Barcelona have had some of the best midfielders in the world. Yaya Toure was one of them. He signed from AS Monaco in 2007 for a fee of £8.1 million.Thanks to his box-to-box abilities, intense work rate, strong physique and impressive passing, Toure was a machine in midfield for the Blaugrana. He was a key part of the team that won the continental treble in 2008-09 under Pep Guardiola.His impressive performances attracted attention from Manchester City, who were then newly taken over by the Abu Dhabi Group.FC Barcelona@FCBarcelonaGAL OF THE DAY @YayaToure1:30 PM · Dec 27, 202112449875G⚽️AL OF THE DAY 🙌 @YayaToure https://t.co/svWDbLg1qbToure was sold to the Premier League club in the summer of 2010 for a fee of £27 million, making it a profit of £18.9 million for the Blaugrana. The Ivorian midfielder went to achieve more success with City.#4 Jasper Cillessen - £19.8 millionJasper Cillessen struggled with game time with the Spanish giants.The Dutch goalkeeper performed very well at Ajax, prompting encouraged the Blaugrana to sign him to replace the outgoing Claudio Bravo. Jasper Cillessen was signed for £11.7 million in 2016.Although his major contribution for the club came in domestic cup competitions, the Dutchman proved his worth. He won the La Liga and Copa Del Rey twice with the Spanish giants before leaving for more regular football.SPORTbible@sportbibleJasper Cillessen played the Copa del Rey final with Barcelona against Valencia and lost itThen he moved to Valencia and at the weekend he received a guard of honour and celebrated the trophy that he lost with Barcelona. His face 6:21 PM · Aug 19, 2019228104866Jasper Cillessen played the Copa del Rey final with Barcelona against Valencia and lost itThen he moved to Valencia and at the weekend he received a guard of honour and celebrated the trophy that he lost with Barcelona. His face 😂 https://t.co/O5XF6pK5dyCillessen joined Valencia in the summer of 2019. The transfer fee involved was £31.5 million, helping the Blaugrana make a profit of £19.8 million with his sale.