The Eagles confirmed the transfer:
As reported by Jonathon Rogers of Crystal Palace's official website, the forward pointed to Eagles manager Alan Pardew as one of the key factors behind the move:
I spoke to the manager and he really wants us to be competitive and score goals. It was really important to know the manager and it was a good decision for me, and I'm very happy to be here.
We had a good time together [at Newcastle] and I'm pleased to be back under him because I think he is a very good manager. He can give me a lot, and I hope to do the same for him and the team.
The France international made the most of his opportunities in his first season at Stamford Bridge, scoring seven Premier League goals while starting just six matches, per WhoScored.com.
But despite his solid performances, former Blues manager Jose Mourinho gave the 29-year-old few chances to show he could be a starter, even when Costa struggled for form early in the 2015-16 campaign.
Former interim manager Guus Hiddink turned his attention to the transfer market in January, sealing a loan deal for former AC Milan star Alexandre Pato. The move indicated the Dutchman may not have rated the forward highly, and new Chelsea head coach Antonio Conte clearly feels the same way.
The Italian brought in Michy Batshuayi, who has impressed early on in his Blues career and seems set to take on a bigger role as the year progresses.
Remy did an admirable job leading Newcastle's attack during the 2013-14 season, showing he's more than capable of being an everyday starter for a Premier League club.
Palace are winless after three Premier League matches and have scored just one goal, and the additions of Remy and Christian Benteke should help in the scoring department.
Financially, it makes sense for Chelsea to cash in now, but one has to wonder whether the Blues will end up regretting this move. Costa has struggled with injuries in the past, and depth is now limited behind him.
Change was needed after an abysmal 2015-16 campaign, however, so it shouldn't come as a surprise to see the team part ways with a fringe player who wasn't expected to contribute much. Remy is still a solid forward and an investment the Eagles shouldn't regret.