That is the question. I think there’s a saying that you (often) regret most the things you didn’t try or attempt in life - rather than the ones you did. Even if you failed or didn’t like the result in hindsight.
Broth‘s colleague got to scratch the itch he had - had he not done it and least tried it, his regret might have been much greater.
Aren’t they already exposed to a different culture through your wife?
Personally, I‘d ask a another question, in addition to the thread title („benefits of (being an) expat“), namely your intrinsic desire and motivation to go to the place/country:
Have you always want to work abroad „wherever that may be“ (Congo, Nicaragua, Eastern Siberia) or did you have places in mind? Do you want to live in China. Can you envision yourself liking it? Are you interested in Chinese culture, etc.? Or you rather indifferent band China’s something you may just be considering due to practically being offered the opportunity!
I am certainly not one to diagnose you from afar. But I am going to say that „cultural exposure is always good“ and „hopefully they’ll have to pay me good money“ along with the notion of „almost no one qualified would be willing to go to China“ doesn’t strike me as having a strong desire of wanting to move there. And the cultural exposure and money may just be ways of supporting the idea by rationalising it (to yourself).
Then again, maybe you are the adventurous type, your family would be all up for it, and have just a little doubt remaining about the economics of such a move? Or you always wanted to be an expat and will always have that nagging regret if you don’t do it?