Means the "typical" cost of housing in HK, according to the figures above is : $23k x 13months payment x 6 (taking the upper limit) = 1.8m
Another way to estimate a "health" supply-demand housing market normally by the the banks is :
Monthly mortgage mayment <= Household income medium x 40%
i.e. 30k (for a couple, used by bank at the moment) x 40% = 12k
In current intrest rate 12k monthly mortgage payment equals to around 1.5m-2.0m. It is about right and confirm to the above scenario.
For a typical 1.8m flat of 500 sqft, the 'typical' market rate is $3,600 per sqft. Anything more than 25% of this figure, no matter in urban or sub-urban area, means a distorted market away from the healthy market driven situation, ie bubble.