And by the way, the correlation between mining cost and price is that price comes first, out of the minds of the market actors. The cost of the coins will match that price.
Price come first because the market always looking forward 6 months, the price for bitcoin is always a projection of the mining cost per coin 6 months later, by smart investors
Let me try again. The value of a bitcoin originates in the minds of
all actors, including buyers, sellers, sellers of goods, hoarders, asic manufactures, bitcoin pole dancers..., taking into account
everything, including the present and the future. If some actors's values cross each other, there will be a trade and hence a current price. The cost of mining is derived from that price.
Your theory is the labour value theory, capital being condensed labour. It has been refuted for centuries.
There are smart investors who know what is really happening behind the scene and they could project the future price with high precision, they buy coin before it is too late. Their purchase will push up the price inevitably, so when you see a steady rise in exchange rate, you know that difficulty will rise soon
It is easy to project the sharp rise in difficulty if you know BFL is going to put hundreds of thousands of ASIC devices into market in the second half of the year. But this only becomes clear when Avalon first delivered their ASIC at the end of January. Following Avalon batch 1 delivery in February, all the uncertainty about ASIC devices were gone, exchange rate started to explode
And just like marcus_of_augustus said, the cost of mining act as a reference of the coins exchange rate (if the cost is higher than price of the coin, miners will shutdown rigs and buy coin directly, their buy will raise the price)
We suppose that people always want to get coins, and they can get coin through either mining or buying, mining decided the lowest possible cost for a coin
