Since Roman Abramovich's arrival at Stamford Bridge in 2003, Chelsea have never been scared to splash the cash.
One of the richest clubs on the planet, you'll often see Chelsea throwing big money around, but they don't always get the kind of return they'd want from such expensive acquisitions.
Let's take a look at Chelsea's ten most expensive signings of all time and whether each was a hit or a miss.
10. Mateo Kovacic (£40m)
After initially joining on loan, Mateo Kovacic sealed his permanent switch to Chelsea during their infamous transfer ban of 2019.
The Blues' Player of the Year during Frank Lampard's sole full campaign, Kovacic has flashed his class regularly at the Bridge and is popular among fans for his mazy runs and inability to understand the concept of pressure.
Questions over his consistency and ability in the final third will continue to be directed towards Kovacic, but overall, Chelsea fans are happy with the Croatian.
9. Ben Chilwell (£45m)
Lampard made it clear he wanted Ben Chilwell to replace Marcos Alonso and Emerson as Chelsea's left-back, and he got him eventually. Leicester wanted £70m but the Blues got their man for £45m.
We quickly saw why Lampard was so determined to bring him in as Chilwell enjoyed a red-hot start to life at Chelsea, and although he lost his spot following Thomas Tuchel's arrival, he soon won it back.
A clear upgrade defensively, Chilwell has been everything Chelsea needed.
8. Timo Werner (£47.5m)
How do you sum up Timo Werner's time at Chelsea?
On one hand, he bagged six league goals in his debut year, 22 fewer than he recorded in his final Bundesliga season. On the other, he was an assist machine and ended the year with 27 goal involvements in all competitions.
He has been a good player, but the fact that Chelsea had to chase a new goalscorer 12 months after signing him proves that Werner did not live up to expectations.
7. Jorginho (£50m)
Lured over from Napoli alongside manager Maurizio Sarri, it was a rough start to life at Chelsea for Jorginho.
Seen as the boss' favourite son, Jorginho attracted a lot of the blame for Chelsea's uninspiring performances, and he wasn't helped by the fact that Sarri refused to drop him.
Since Sarri's departure, however, Jorginho has been excellent. Under Tuchel, he dominated en route to Champions League glory and is in the conversation for the 2021 Ballon d'Or.
6. Fernando Torres (£50m)
Fernando Torres was doomed from the start. When he joined Chelsea in January 2011, he was already on the decline, but the Blues' willingness to throw £50m at Liverpool to sign him raised the bar far too high.
Having said that, Torres fell very, very short.
To his credit, Torres worked incredibly hard for Chelsea and never gave up, despite missing sitter after sitter after sitter. He was abysmal in front of goal but gave his everything for the club.
He didn't do too much for Chelsea, but his goal against Barcelona in the semi-final of the Champions League almost justified his whopper of a transfer fee. Almost.
5. Christian Pulisic (£58m)
Despite Chelsea's determination to have you believe otherwise, Christian Pulisic was 100% brought over from Dortmund in 2019 as the replacement for the soon-to-be-departing Eden Hazard.
He joined up with the club that summer and spent his first season combining electric form with never-ending injury struggles. His highlight came after the first COVID-19 lockdown, when Pulisic spent a few months looking like the best player in England.
At this point, the jury is still out on Pulisic. He does a lot of fun stuff, but not as often as he probably should.
Verdict: Miss... just
4. Alvaro Morata (£60m)
Antonio Conte wanted a new striker after binning off Diego Costa because he was a little bit mental, and after the board failed to bring him Romelu Lukaku, he eventually settled on Alvaro Morata.
For a few months, the move looked like a stroke of genius. He had six goals in his first six league games and sat on ten by December, only to then manage just one more goal over the remainder of the season.
Injuries and a crippling lack of confidence saw Morata lose all ability to score goals, and Chelsea decided they could take no more than 18 months of him before loaning him to Atletico Madrid.
Verdict: Like every shot he took, it's a miss
3. Kai Havertz (£71m)
Kai Havertz moved to England at the worst time possible. Billed as the next big star of the Premier League, the young German took a little while to get settled in a new country and then contracted COVID-19, which continued to bother him for months and months.
The 'flop' label was (understandably) being thrown at him, but he started to find his groove towards the end of his debut season... just in time to score the winner in the Champions League final.
Chelsea fans know there is still a lot of room for improvement from Havertz, but thanks to his form towards the end of 2020/21, there are plenty of reasons to be confident.
2. Kepa Arrizabalaga (£71.6m)
Left panicking by Thibaut Courtois' move to Real Madrid, Chelsea chose to trigger the £71.6m release clause of Kepa Arrizabalaga in 2018, making him the most expensive goalkeeper in history.
After a solid debut season, which brought us his infamous spat with Sarri, Kepa's form plummeted to an ungodly low. 2019/20 yielded some of the worst goalkeeping statistics the Premier League has ever seen - it felt like every shot he faced went in.
Lampard was adamant that he needed replacing, and that's exactly what happened as Edouard Mendy came in in 2020, dropped Kepa to the bench and went on to win the Champions League.
Verdict: Huge miss
1. Romelu Lukaku (£97.5m)
Chelsea decided they needed to go hard in their pursuit of a new striker, so they obliterated their transfer record with a £97.5m move for Romelu Lukaku.
The Belgian returns to Stamford Bridge ten years after he first joined, and there is a real confidence that he could be the missing link in a side who just won the Champions League.
He bagged 24 goals in his final season in Serie A, but how many will he manage now he's back in England?