How can I multiply a parameter by quantity (called Count in Revit)?
Strictly speaking you can't! (correct at the time of writing - November 2014) However by adding in parameters and being selective about data grouping and sorting options we can get around Revit's reluctance to help. Unticking itemise every instance will make Revit sneakily do it by the back door! Add some cost values to your components within the schedule and see Revit 'do the math'.