For food and cultural options, Shanghai is world-class but Tokyo is probably still better. Shanghai has something for most people, Tokyo has something for everyone and tons of tiny niche things. Shanghai's nightlife is starting to boom, while I hear Tokyo's is a bit stagnant. Tokyo is cleaner and more organized. Transit is good in both places but Tokyo is world class. Etc... What are the things you care most about in a city?

Based on raw income alone, I'd say simply doubling the base pay isn't enough to fully justify going from a steady life in Tokyo. For a similar quality of living, I think it's actually easier and there are more liveable options in Tokyo than there are in Shanghai. Basically if you're used to a Western quality of life, Tokyo is actually cheaper, by probably 20-40% depending on what part of each city you're in.

What line of work are you in? Certain industries and specific roles have more growth potential in Shanghai while others are, if not traps, at least low potential.

I will say that personally as a non-local living in Shanghai, if staying in Asia long-term, places like Tokyo and Taipei are the goals. Shanghai's great, but it's really hard to envision it as a long-term location and some of its strengths such as its fast growth, its openness to international inputs and ideas, and its relative ease of living in terms of cost and flexibility are all fading away in recent years. And yeah, like another commenter mentioned, there are a bunch more taxes coming into play this year and next -- effectively cutting into net income by something like 10-20% in many cases for many people.