The Greater Bay Area’s GDP of around $US 2 Trillion makes it the 8th largest in the world, ~ the size of Canada. Despite which, my reading is that hongkongers are pretty leery of getting involved in the GBA. Partly because wages are still much lower than in Hong Kong.
In the pic above, that’s not the Hong Kong skyline, but Shenzhen, across the border into China. Which, when I first went in 1976, was rice paddy fields. Now a city of ~13 million. The green area is Hong Kong land, in the northern New Territories.