3932458 DA smog pump pulley
 

Why are these so expensive what do they fit how rare are original ones

I Know (asking) 2,500 dollars for a Pulley is Plain insulting.
Sellers can jump in a lake in my opinion.
Unless you are under some Very Very serious judging situation I would think the repops are fine. There had to have been domestic mfr. Reproductions from the Goat Hill Days of the 1990 floating around.