Yes HK is expensive, but so are the other countries offering high FO contracts
Your location says USA PA Dude, so although I'm not from the US, I'll try to put it into a perspective you know.
HK is considered one of the most expensive cities in the world, especially for expats. The big one is housing - this place is more expensive than New York. Look at the package, and consider if you could live in N.Y. on it. And by N.Y. I'm talking about Manhattan, not the outer suburbs. In the US, you might have the option to live out of town & commute to the city, not so in HK. You can live in Tung Chung, 30 min train from the city, 5 min to airport, but there's not a lot there. And it's still outrageously expensive.
The salary sounds big but so are the costs.