GDP produced divided by costs required measures intensity. These will be typically normalized (inflation removed) or, if a ratio, can be nominal since both have the inflation ratioed out.

GDP is known to be an imperfect measure, especially for capturing cottage industry and due to the distribution effect you described, but it's not horrible to start with.

GDP is how much wealth is produced in society at a moment in time.

The total accumulated wealth in a society is a related but entirely different number.