Goalkeepers are the last line of a team's defense. So it's imperative that title-winning teams - be it in league or international football - need to have quality custodians in place.Over the years, especially in the last two decades, the goalkeeping position has evolved a lot. It no longer suffices for a team's goalkeeper to make saves and keep their citadel intact. Goalkeepers have become an essential part of a team's offense, building attacks from the back in a quintessential sweeper role.The likes of Victor Valdes, Manuel Neuer and Alisson Becker, to name a few, have played key roles for their respective teams in winning league and continental titles. On that note, here's a look at the five most expensive goalkeepers in the game's history.#5 Jasper Cillessen (Valencia/Netherlands) - €32 millionJasper CillessenValencia acquired the services of Jasper Cillessen from Barcelona in the summer of 2019. But the Netherlands international has played only 31 games in all competitions, missing large swathes of last season due to injury.However, Cillessen has shone in Oranje colors, recently becoming only the fifth goalkeeper to make 50 appearances for the team.50 - Jasper Cillessen is set to become the fifth goalkeeper with at least 50 caps for the Netherlands. Guardians. pic.twitter.com/U24ejHoLRM— OptaJohan (@OptaJohan) June 9, 2019Previously, Cillessen, a ball-playing goalkeeper, arrived at Barcelona from Ajax and was renowned for his ball-distribution prowess and ability to operate in high defensive lines.But during his three-year stay at Camp Nou, the Dutchman mostly played Cup games and struggled to keep out penalties, making the first save of his career in 20 attempts during a 2019 Copa Del Rey game.Cillessen was famously subbed out for Tim Krul just before the Netherlands' 2014 FIFA World Cup quarter-final shootout against Costa Rica, which they won. But the Netherlands couldn't do so in the semi-final against Argentina and ended up losing.#4 Ederson (Manchester City/Brazil) - €40 millionEdersonManchester City dished out €40 million for Ederson's services in the summer of 2017. Four years later, it is safe to say that the Brazilian has been one of their best-ever investments in recent years.The 27-year-old has become an integral part of Pep Guardiola's all-conquering City team, winning three league titles during his four years at the club. Ederson has kept an impressive 95 clean sheets in 192 games in all competitions for the club, keeping at least 17 shutouts in each of his four Premier League campaigns.It is clear to see why the Brazilian has been Guardiola's first-choice keeper since arriving at the Etihad. Ederson is a quintessential ball-playing goalkeeper, which makes him a great fit in the Spanish tactician's system.🅰️ Ederson is the first Premier League goalkeeper to register an assist this season and the fifth in Europe's top five leagues😂 He now has three assists in his Manchester City career pic.twitter.com/hPRjFZEn1l— WhoScored.com (@WhoScored) February 13, 2021Ederson, who played four games for Brazil at Copa America 2021, has an impressive record for his national team too, keeping ten clean sheets in 16 games. But his failure to do so in the final against Argentina cost Brazil the Copa America title, although there was little he could have done to keep out that Angel di Maria finish.