Mainly due to the time involved to assessment, interpret and write up the information. As outlined in the assessment steps there are several processes involved in conducting an assessment. Each of these steps involves time from the psychologist to complete the work involved in the assessment. Piecing together the results from the measures along with other supporting information is a complex process which 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.