It looks like you have misplaced parenthesis in your cart object.
Open your shopping cart definition and go to the "Calculations" tab. Select the TotalPrice calculation.
You have it set to:
([Price]+[SizePriceInc]+[InletPriceInc])+[BafflePriceInc] * [Quantity]
but it should be:
([Price]+[SizePriceInc]+[InletPriceInc]+[BafflePriceInc]) * [Quantity]