Does bargaining Affect magic item components?

Hey, just a quick question.

Was thinking about magic item creation and buying monster parts, it occured to me that as bargaining means a 10% reduction in price for the monster parts (they are basically a commodity), then it makes just as much sense for the rest of the components to also be reduced by 10%.

Given that the base cost of a magic item is quite likely things which you have to purchase from people, it makes perfect sense to me that you should be able to get 10% off either the base price or 1/2 the base price of a magic item you're creating (so a Sword +1 costs either 4500gp or 2250gp to create at base cost).

Is this incorrect?

Makes sense to me.