Make that "HK postal rates were so cheap." There've been heavy increase in recent years. The only relative bargain remains the e-express packet, and those rates to the U.S. increased at the end of June.
They are still
extremely cheap compared to other developed countries.
A small letter airmail to US or Europe costs HKD4.9.
The same in France to HK costs EUR1.4 or HKD12.6. From USA to HK costs USD1.15 or HKD9.
The difference for parcels is also 2 to 4 times more expensive from abroad.
This is why the US and some other countries wanted to refuse delivery of HK post items because they were getting a raw deal