Sometimes your opponent can outspend you at every step and is possibly more motivated to achieve its goals. For China this is a far more pressing matter than profit, you might even see it as desperation. So this is like wrestling a bone from a hungry dog's mouth.

On the other hand TSMC is a publicly traded company. There's a limit to what expenses they can justify in front of the shareholders. China can lure engineers away with 3x the salary probably because that was the limit TSMC settled on, not because that's the limit of what China is willing to pay.