I mean obviously the huge financial benefit is the main reason he'd come here from Madrid. Which is fine. That's the reason a lot of players move to a lot of clubs. It's their career after all, not a hobby.
It doesn't tell you anything about how they'll perform or how committed they'll be once they arrive. The likes of Aguero and Silva didn't land where they did because of a deep-seated desire to play for Man City, they went there because of the money. And they performed as well for City as they would have for anyone else.