I think she was motivated by Arcachon's notion that live in HDB for X number of years for "free" and can sell for XXXK higher and just want to do that calculation to be sure.
How about the intangible "gains" like the use of facilities (family usage), parking, rental saved, prestige?
Cannot include every component for calculation. Different components are added for different purposes. Do you want to calculate rental yield or absolute gain/loss? Then must include more details like pricing, years?
The three laws of Kelonguni:
Where there is kelong, there is guni.
No kelong no guni.
More kelong = more guni.