how to compare valium / xanax? why is valium cheap

is it valium 10mg = xanax 2 mg , if you compare strenght?

if so, why is xanax +50% more expensive than valium?
(100 1mg xanax cost as much as 100 10 mg valium, often more) I know that valium is a bit more long-acting than xanax, but is the sime kind of medicines used to the same kind of puropses