And how would they do that?
After all of you and I buy the same new build house tomorrow in different streets in the same town and keep them for 20 years how would you account for the following in your scheme:
I have let my house go to wrack and ruin and done no decorating/landscaping or updates of kitchen bathrooms.
You have modernised, maintained and enhanced with an extension, lovely gardens, bathrooms an kitchens.
The school you are in catchment for is excellent and the school my house is in catchment for is very poor.
The house next door to me has been turned into a funeral parlour.
The road behind my house has been upgraded to a dual carriageway removing all the traffic from your road.
Apart from anything, house prices move up and down with the economy, cost of living, interest rates, government policy, taxation, housing supply, population levels etc.
And finally, if you are looking at what is “unfair” start with the fact that your Dad was in a position to provide both his children with down payments which enabled them to buy houses in the first place. What about all the people whose parents either can’t afford to do that or choose not to.