Why the design of deeper and more concave forged wheel is , the higer quotation will be?

Why the design of deeper and more concave forged wheel is , the higer quotation will be?

Please view the following comparision picture first and know the reason below.

The green-line shape is the spin forge before precision-machining process, and the white shape is the wheel spoke showed after precision-machining.

You'll see the deeper more concave forged wheels you want, the more heavier spin forge  we have to use and the more machining work it requires.