Actually - I would clarify that a bit more and break it down into Junior Mining companies (whom are often not producers but are explorers) which have put up the shutters due to lower commodity prices and a risk adverse investor climate means that they can't attract capital - even if they do have a good story. This is the animal spirits or mindless herd mentality in action. A classic recent example was a Junior Company whom drilled a hole in the NT and got a reasonable intersection of copper at open pittable depth and the share price went down the next day! As always with these cyclical things such as commodity prices and sometimes exchange rates, the movements always overshoot and undershoot the fundamentals and that's where more long term or smarter investors buy in, when most in the market are running around like headless chooks selling at a loss. Lower AUD also encourages foreign buyers to buy Australian companies and their resources as the lower AUD starts to make acquiring Australian resource companies better value, when you start seeing the smart guys like Glencore and the Chinese acquiring Australian resources/stocks then you know the market is oversold and the exchange rate has made mergers and acquisitions a viable strategy for the next commodity upswing.
For the medium sized and larger producing companies - input costs comprise a lot of things from the ongoing price of labour, price of fuel, cost of energy to the one-off cost of new equipment, cost of construction materials and labour and other finance costs. In a lot of cases - provided most of the labour and goods can be sourced in Australia then a lower AUD is generally a good thing - as most final products like metallic ores, coal, oil, gas etc are sold and traded in US$ even though mostly going to China/Japan/Korea.
These equations change a lot with Australian companies listed here but with producing assets overseas - such as mines in Africa, PNG, South America and other overseas locations.
But I digress - the biggest single factor in the AUD exchange rate is still the money printing going on in various parts of the world, and the relatively high interest rates in Australia attracting all that funny money sloshing around the world.
The biggest factor in commodity prices are the larger iron ore producers trying to permanently put the high cost Chinese local iron ore miners out of business, and Saudi Arabia trying to put their higher cost competitors out of business like ISIS, Iran, Russia, Venezuela, US Shale etc
