"It is general valuation practice for sales characterized as comparable sales to be used as bases for the valuation of lands said to be similar. But allowances must always be made before such sales can be so used. No two parcels of land are identical in all respects: the sale price of any given piece of land is not necessarily the price at which it ought to have been sold, or the same thing as its true value. Before using any allegedly comparable sale, therefore, the valuer must consider whether, having regard to the circumstances ... appertaining to the parcel of land in question, and to the transaction of sale, there are sufficient similarities to the circumstances appertaining to the subject land and to the notional sale presupposed by the test formulated in Spencer v The Commonwealth of Australia ... to warrant a court's reasoning from the sale price paid under the allegedly comparable sale, with or without other evidence, to a value for the subject land. Adjustments must, of course, be made every time reasoning of that kind is undertaken. For example, in relation to the land itself and the circumstances appertaining to it, it may be necessary to consider such matters as topography, location, size, shape ... land use (actual and potential), scope for, and difficulties of, development, ...; and in relation to the transaction of sale, the valuer must weigh such things as the character, business and relationships of the parties, their motives, the terms and conditions in their contract of sale, and any other special considerations that induced or may have induced them to conclude the contract at the selling price agreed, as well as the dates when the contract of sale and the transfer were concluded or effected."