Then the situation is going to become a little more blurred.
There are a number of other ways at arriving at a property valuation and Im sure Revenue will accept valuations that are calculated reasonably and with logic.
For example if there are no comparable apartments sold in the area, you might work on the basis of the rent yield. If the apartment rents at 7000 per year, it wouldnt be unreasonable to assume a net rent yield of say 7%, which would imply a valuation of 100000