Because it's RVN. He's approaching the end of a contract with Madrid, so it's likely he's not going to be paying that much a year for him anyway.
Also he's a top notch poacher, if that's what you're looking for. He'd slot in perfectly in my system. His mental stats ensure he'll play better than most other poachers you could find. Not to mention he'd make an excellent tutor for the younger players, and for only 2.3 mill that's really not that much. Sure he's Chelsea and he can buy just about whomever he wants, but for only 2.3 mill I'd be hard pressed to find a better option.
I also imagine RVN has a high reputation on the game, or at least he should, that also often helps, it'll boost income. The bottom line is, you could find a ton of other younger poachers in the game with attacking attributes just as good, but you'll pay a heck of a lot more, and they won't have the mental attributes. I think that's a part of the game a lot of guys overlook.