look at the stock OEM pulley and compare it side by side with the UD pulley. Use your logical sence to figure out which one cost more to be produced. The OEM one has TWO rubber rings built-in and the UD pulley does't. Each OEM pulley is tuned to certain frequency or frequencies before it is installed in the new car. Also mass is added to the OEM pulley for damping purposes. "frequency = square root of (k/m)". All these process cost big $$$ and the increase cost of making the pulley will be charged to the price of the new car. On the other hand, UD pulley is just a piece of machined solid aluminum.
Hmmmm.... Can someone tell me why car manufacturer is so stupid to do this? Spend $$$ to make a heavy pulley which will slow the car and increase the price?