Mainly due to the time required to assess, interpret, and write up the information. As outlined in the assessment steps, several processes are involved in conducting an assessment. Each of these steps requires time for the psychologist to complete the assessment. Piecing together the results from the measures along with other supporting information is a complex process that requires both time and extensive knowledge. As each person is unique, the information must be interpreted based on your specific presentation and results in combination, not simply the responses from the measure alone. The time required to complete this is the reason for the cost.