In a matter of three years and two Premier League titles, Chelsea have more than doubled what they invested to bring Costa to London. In June 2014, he arrived for £32m. Yesterday, Atletico agreed to take him back - for £67m. A club record. So much for those stories of Costa's AWOL antics driving down his valuation. Shave a couple of million off what Tianjin Quanjian were prepared to pay in January and Chelsea have not lost out at all. Marina. Michael. You've done good.
Will we miss Diego from the Premier League? Should we? For this column, both questions deserve a resounding yes. All the rows. The bust-ups. Don't tell us you haven't enjoyed following it.
In England, Costa was a throw back. The nasty, spiteful, in-your-face centre-forward who became legend in British football. Joe Jordan. Billy Whitehurst. Mick Harford. Okay, they were no divers like Diego, but there were definite similarities in their approach to the game. And like those three, Diego will go down a cult hero.
Yes, he's no Didier Drogba. But who is? And it's a fair point to compare how Drogba created a legacy at Stamford Bridge while Diego didn't give a second thought to his. Both centre-forwards made history with Chelsea. Both were feared, for some despised, by opposition fans. But it will be Drogba who will be forever loved by the Blues support. For Diego, the idea of legacy just doesn't enter his head.
That anecdote we've mentioned in past columns about Diego's first tour of Stamford Bridge still warrants an airing and really sums up what he brought to English football.
Given a tour of the stadium by Cesar Azpilicueta on his first day, Diego stopped them both when on the Stamford Bridge pitch. "Bring me the toughest guys here," he demanded of Azpilicueta in Spanish.
In broken English, Diego looked the three in the eye and said in broken in English: "Are you ready to fight? Are you ready to fight with me?"
Terry, for one, loved it. Here was a fellow warrior. And in that first season with Diego, Chelsea finished champions.
If you had a ticket to see Chelsea and Diego was in the team, you knew you'd be getting value for money. A Premier League match featuring Diego was no routine affair. He left you with an experience. Memories. Fighting with the opposition. With teammates. With his manager. There was always a bit of electricity around Diego. Bib-gate. Pedro. Conte and Leicester. C'mon, you're saying you didn't enjoy that?
Diego was made for the Premier League. No-one can deny that. A headline act in the most entertaining competition in the world. He was the panto villain. The one we all hated - but none of us could ignore. The media. The fans. We'll all miss him. Well, maybe not all...
This is a stunning piece of business by Chelsea's dealmakers Marina Granovskaia and Michael Emenalo. There was only one destination Diego wanted. He was refusing to leave his Lagarto home in Brazil until the deal was done. Everything, it appeared, was in Atletico's favour. Enrique Cerezo, the club's president, seemed to hold all the cards.
Yet, Chelsea are the big winners out of all this. More than doubling their money. Ridding themselves of their one nagging problem. And after that opening day defeat to Burnley, they're unbeaten. Alive in the Cup competitions. And have been able to negotiate from a position of strength. Diego Costa? Chelsea have moved on - and are a cool £67m richer for it.
Diego is now Atletico's problem. And while the likes of Koke and Filipe Luis are happy to welcome him back, the locker room has changed since he was last there. Antoine Griezmann is now their biggest name. The Frenchman arriving as Costa was sold to Chelsea. Will they get along? Can they play together? What of Fernando Torres? Does the favourite son meekly step aside? Will the fans support it?
There's some issues there for Diego Simeone, the Atleti coach, that he'll need to confront. And that will include Diego's fitness and lack of preseason.
For Atleti and Simeone, this isn't going to be straightforward. But then again, it never is when it comes to Diego.