I assume that the Deputy is referring to a self-build residence and that by cost price he means the cost of building the residence.
I am informed by Revenue that the loan-to-value ratio used under the scheme is calculated as the amount of the qualifying loan taken as a proportion of the purchase value of the self-build residence.
The purchase value of a self-build property is the valuation of the residence that, at the time the qualifying loan is entered into, is approved by the qualifying lender. This includes the aggregate of the market value of the land and the estimated costs of construction, as applied by the Central Bank when they calculate valuations for the purposes of the macro prudential rules.