An owner may not simply echo the phrase "fair market value" and state a number to substantiate the owner's claim; the property owner must provide the factual basis on which the opinion rests. This burden is not onerous, particularly in light of the resources available today. But, the valuation must be substantiated; a naked assertion of "fair market value" is not sufficient. Even if unchallenged, the property owner's testimony must support the verdict, and conclusory or speculative statements do not. In addition, under this court's precedent, evidence of the amount paid in the past to purchase property, by itself, is legally insufficient to support a finding as to the property's market value at a later date.