There are two fundamental reasons for the "time and effort" rather than valuation method. First is the fact that the differences between any two properties make it impossible to relate the complexity of the task to the value of the property. A high-end property could be a relative "no brainer" while a particular mid-market home could have dozens of variables to be analyzed. The second reason is that basing fees on value places an obvious incentive on appraisers to estimate high, thus distorting reality.