Calculation Errors/variations

I have extracted a list of costs against an ID. When the columns are added up via slice and dice at the bottom of the table the answer comes to 242,689.99 (formula: =Sum(<CST_Alt Cost(Query 3 with MCPCF23A)>)). However, if I insert a cell (Insert, Cell) to provide summary information at the top of the report and insert the same formula I get a completely different result - 137,174.15.

Any ideas out there?