Delph would have been bought for his passport too, and he knows it.
I doubt he'd be on 60k more, 40k more sounds closer. And he'd be at the mercy of Man City using their limitless budget to bring in a midfield superstar to take his place in the queue.
Money-wise it's a no-brainer, but it's a big, big risk football-wise, and who knows, maybe loyalty was even a small factor?