I think it’s 30%-40% the cost of smelting it. Unless you can drop the price of energy and cheapen the raw material cost, the entire manufacturing industry will be uncompetitive.
Primary smelters currently run pretty efficiently but are bottlenecked by two main factors in the USA: raw energy prices and regulations. (there’s likely some modern process improvements they could add too but those won’t increase productively as greatly).
To reduce energy costs… you’ll need about double the current energy production we have today. That sounds like a lot but it’s very doable (the US has been neglecting itself for 50 years). It could with a little push from the Government catch up in 10-15 years, think lots of nuclear and solar.