>I thought that as long as the computed column was deterministic (something like total AS (Qty * Price)) then it would be calculated at INSERT or UPDATE time only and the column could be used as an index and then optimizable...
There is no need of calculation. At least not by you. You could use "Computed" column and put formula there. This is SQL Server :-)
Against Stupidity the Gods themselves Contend in Vain - Johann Christoph Friedrich von Schiller
The only thing normal about database guys is their tables.