With a club-record 257 goals to his name and 10 major trophies secured since his £38million signing from Atletico Madrid in 2011, City have certainly got their money's worth.
Many could argue the prolific Argentinian actually repaid his fee several times over in the act of scoring just one of those goals, however.
That came in 2012, when Aguero struck not only the most famous goal of his glittering career, but arguably the greatest in Premier League history.
In the most sensational finish the competition has known, Aguero etched his name firmly into City folklore as he struck the goal that clinched the title with virtually the last kick of the season.
City had been trailing 2-1 to QPR heading into injury time of their final game of the campaign, apparently handing the crown to arch-rivals Manchester United.
Yet they turned it around in dramatic fashion, first with an equaliser from Edin Dzeko and then Aguero's remarkable late, late intervention.
Taking a return pass from a prone Mario Balotelli, Aguero burst into the area, skipped round a defender and smashed the ball past Paddy Kenny. The clock read 93:20 as Aguero wheeled away whirling his shirt around his head as pandemonium broke out on the touchline and in the stands.
City had snatched the trophy on goal difference at the death, capping an extraordinary title race which had already seen plenty of twists and turns in a manner that was scarcely believable.
It was the club's first title in 44 years and pipping United at the post made it all the sweeter.
So, whenever Aguero returns to Manchester in the future it will be this goal, above all, that people will want to talk to him about.
Yet while it may begin many a conversation, it is unlikely to end them for there is so much about Aguero's brilliant City career to discuss.
He arrived with a bang with two goals – one of them spectacular – against Swansea on debut and he scored with great regularity thereafter. There have been stunners and tap-ins, volleys and headers. There have been 16 hat-tricks, including a sensational five-star display against Newcastle, two trebles against Chelsea and a memorable three-goal hit against Bayern Munich.
There have been plenty of milestones along the way, most notably when he scored against Napoli in 2017 to overtake 1930s star Eric Brook as City's all-time leading goalscorer with 178. He went on to become the first City player to pass 200 the following year. In Premier League terms, he is the competition's leading overseas goalscorer with 181 – a figure that puts him fourth overall behind Alan Shearer (260), Wayne Rooney (208) and Andy Cole (187).
There have been challenges too, the biggest being after the arrival of Pep Guardiola as manager in 2016. After thriving as an out-and-out striker under Roberto Mancini and Manuel Pellegrini, Aguero initially seemed an uneasy fit for the Spaniard's more demanding style in which pressing opponents and playing a bigger hand in build-up was more important.
Speculation over his future ramped up after the arrival of Gabriel Jesus, a forward seemingly more in tune with Guardiola's thinking, but he responded by improving his all-round game and once again becoming indispensable.
If there has been a flaw it has been a surprisingly indifferent record from the penalty spot. Injuries have also frustrated him too – muscular problems in the early years which prompted a change of diet and lifestyle, and knee trouble in more recent times – but these are mere footnotes in a great career.
He will leave City having posted statistics that may not be beaten for many years – and scored a goal that for many never will be.