Not that I am saying you are wrong, but I buy Jade for the Jewelry stores back in the states. The place I was referring to does not sell neophrite only Jadeite.
I visited their cave where the raw blocks are mined and the factory where the stones are cut and polished.
Initially I didnt trust "China" suppliers, so I tested each shipment for mohs, clarity, and chemical treatment. After a few large shipments without any problems, I learnt that I could trust this supplier.
The retail margins on Jade are very very high, somewhere in the neighborhood of 1000% markup. About 95% of the chain stores in HK source from China due to its close proximity to Burma, the remainder source directly from Burma and cut their own stones. But those are custom made pieces that people special order and not the ones you see in the showcases.
If you want, I can bring you to SZ with some tools to show you the difference between real and fake jade.
As for the mainlanders coming to HK to buy Jewelry, the current exchange rate favors their currency and due to the high amount of tax/tariff on precious metals, computer equipment, electronics, furs, imported name brand goods like Rolex, Omega, etc its cheaper for them to spend RMB in HK to buy Jewelry.