#3 Christian Pulisic (2019, €66 million)
Chelsea were in the market to replace the outgoing the Eden Hazard in January 2019, as there was an air of inevitability around the fact that the Belgian superstar would finally get his dream move to Real Madrid at the end of the season.
In the meantime, the Blues wasted no time in signing a replacement, as they agreed a big-money deal with Borussia Dortmund for the signing of Christian Pulisic, with the American agreeing a deal in principle with the club at the time.
After a slow start to life in England, Pulisic scored a brilliant hat-trick against Burnley in October, as he announced himself to the Blues faithful in some style. Since then, American football's hottest commodity hs blown hot and cold but he remains an integral part of Lampard's set up, as Chelsea look to move into a new era after the loss of Hazard.
While the 66 million transfer fee could be termed excessive, Pulisic's talent is unquestionable and he's shown glimpses of his potential in his time at the club so far. The 21-year-old has a bright future ahead of him and looks all set to become a pivotal player for the club in the future.