I believe you could buy 20 USB Block errupters for 1 BTC few months ago when 1 BTC = 150. Surprisingly (for you) you coud buy 20 USB Block errupters for 1 BTC few weeks later when 1 BTC = 600.
If you make the whole supply chain in one currency, it really doesnt matter how much it is trading against another currency.
You didn't get the point. Mining Equipment is pretty linked to BTC, so that is a bad example of real world usage 'cause errupters value rises with demand rises with BTC value.
In the end someone had to buy those erupters from a factory, paying electricity in fiat, paying employes in fiat, paying resources in fiat - so there has to be a stable BTC/Fiat relation - which is not the case. So, for not-directly-BTC-related products BTC is completely useless because the lifecycle of a product (production/distribution/sale) is an unpredictable period of time for BTC value. So there is no chance for any product without massive(!) profit-span to get created/sold solely at BTC level. (except short lifetime products or just in time deliveries - which both is rare)
I know, that most of the current BTC-"Fans" are not aware of this, because they may have no idea how product cycle actually works and what makes a currency valuable at all. A highly volatile currency will drop in price because noone (no merchant/manufacturer) is willed to use it. Simple as that. Do not believe me? Well then visit the next factory and ask if they will produce something for you in exchange of iPads. iPads have a distinct value, but the manufacturer just dont care, because he cannot pay his employes in iPads nor can he pay his bills in iPads. Get the point?
And as long as this problem is not solved for BTC or any other Crypto, no crypto will ever be successful in big scale thinkings.