The price fluctuation in aluminum is statistically insignificant and is in fact slightly cheaper today than it was at the first of the year: http://www.infomine.com/investment/metal-prices/aluminum/ Year-over-year, aluminum has been very stable. Look at the five-year chart. Some peaks there, but unless you are building big items, the cost difference isn't significant.
Not saying you are wrong but there is more to it then what this graph shows. The graph looks wrong by about .18/Lb first off based on yesterdays close and today's open. At least in the west Aluminum is supposed to be traded on the LME. There are a lot of variables, like what type, what form, but like I said, the graph appears skewed a little vs. our numbers and for us in the USA a major price adder is missing. The mid-west premium is not added. This geographical adder is added to all sales. That adder has fluctuated from .06/Lb upwards of .20/Lb in the past decade...I know of a .14/lb adder in the past 3 years. So based on a range of .98-1.35 lb I would consider that a huge swing- over 35%.
Now what rules China plays by? Who knows, but what I do know, is that if production was here, and the supply of raw material then pricing would definitely change and quite rapidly even without tariffs. I know today our July Aluminum is around .99-No MW Adder. There are also fab costs but that is a by supplier/stock add in.
Even steel has moved pretty crazy the past 3-4 years.
I would think smart companies have some room built into their price but it can be very tough based on how you handle inventory/sales/etc.