3. Cheap option

Arsenal's initial backup goalkeeper target was Espanyol's Joan Garcia, who was viewed by many as a suitable long-term successor to Raya, but also would have cost €25m. While he is a talented shotstopper, that would have been a lot of money to be splashing on a second-choice in a summer where world class signings in other positions are the priority.
Barcelona swooped in however and are reported to have agreed a deal with Garcia, meaning he won't be playing his football in north London next season. That prompted the Gunners to turn their attention to Kepa, who proves to be a much cheaper option due to his £5m release clause.
That is a bargain the club simply can not afford to look beyond. He is a 'keeper with great experience and can offer a lot between the sticks and the cheap amount he can be acquired for will leave plenty of funds for Arsenal to ensure they make their priority signings.