Just use the current rental price to compare with the monthly payment on the current mortgage rate (i.e.rate 5.5%; 30% for first instalment and divided into 20 years for payment). In fact, it is only a roughly calculation.
For example, as my personal case:
I rent a flat for $16,000
The current price of the flat: $6.2million
30% first instalment will be 1.9m
70% mortgage: $4.3m x 6880 (according to the mortgage table which is on the rate 5.5% for 20 years)
The monthly payment should be: $29,500
Of course, some of the payment is used to cover the capital. But I will also consider the interest for my first instalment($1.9m),it can gain interest if I put it to bank or other investment. Maybe everyone will have their own calculation. This is only my points of view.
It's Royal Ascot in Shatin. It seems it is not a good idea to buy a flat here if the comparisions between rent and sale have such difference. Unless, the rental price raise up 20% or the selling price drop down 15% in the coming future. I like this place and want to buy a flat here, but I am worry the price will drop rapidly if no a reasonable rental price to support it.
?-(