It is the other round. If Build-Then-Sell concept is implemented, all additional costs like interest and construction risk will be passed on to purchasers by factoring it into selling price. Also with this BTS, people will feel that 2nd hand properties have no much difference from 1st hand properties, thus this will push up prices in secondary market. Overall, BTS will only push up both 1st hand and 2nd hand properties.

BTS is to remove risk of purchasers from purchasing an abandoned project and dismiss developers without sound financial, but it cannot be used to control prices.

What I mean is the construction cost fluctuation risk/cost overrun. All these will be factored into initial selling price definitely.

Normally valuers use comparison method based on actual transacted values around the same area. But the actual transacted values are registered 6 months later. That means valuers can only track transactions completed 6 months ago or even longer. Thats why nowadays in a lot of areas valuers value can never match sellers value.