I can speak for Hong Kong, the return on investment on a rental property is around 2.5% (in the case of the apartment I rent it's 2.6%). The reason why rent is so cheap is I believe due to a lot of speculation by people buying in the hope that the price will increase. But this creates a lot of landlords who want to rent and unfortunately for those renters the people renting can only pay so much a month.
Landlords still expect to make a profit with the rising prices though so think that the rent being this low is not an issue but between the NSL and the changes by mainland China, it's unlikely their bet will pay off
I've seen a similar situation in Malaysia where there's a massive amount of speculative investments in luxury condos leading to 38% of the luxury condos being empty. The landlords are just buying it for speculation they don't expect to make money with rentals and that drives the prices of rentals down
1. Price speculation. Owners are willing to take a loss each month assuming they will make it up on appreciation. This is very true for condos in Toronto for example. Rent is about $500-1000/month less than carrying costs of ownership.
2. Long-term ownership. Landlord bought the property for half the current market rate so carrying costs are way lower than if you’d bought today.