While you may be correct, I was referring to extruding, not smelting.
Raw aluminum is a commodity. Typically, when buying extruded to order aluminum profiles on an ongoing basis, one would pay for the aluminum/billet based one whatever the current price is (typically based on the LME), plus the conversion cost (or the cost to push it) which is a constant that you lock in with a contract.
The extruder can control their conversation cost, but they have no control of the aluminum cost.