Suppliers can not go lower than the ROI of 12 months of the mining cost "thats why BTC didn't drop lower than ~2$", and can not go higher than the ROI of 3 to 4 months of mining cost "thats why BTC highest traded price during the last year was ~7.2". But today the equation has changed with the ASIC expected delivery date! GPU and FPGA miners has to return the investment in a shorter time frame. Such time frame is geting shorter every single day.
Do you have any facts that support these satements?
How is $2 related to some 12 month ROI?
How is $7 related to some 3 month ROI?
Why can suppliers not go lower (or higher) than 12 months ROI?
"The price of Bitcoin is usually related at a certain level to the expenses involved in producing 1 BTC. "
Did it cost 32 dollar to make one bitcoin in June 2011? Nope.
Did it cost 2 dollar to make one bitcoin in November 2011? Nope.
Then why do you think it is true now?
Most people mine with GPUs from day one.
Also, the most efficient GPU for that job was available when bitcoin boomed last year.
Yet the price managed to fluctuate between 32 and 2 dollar.
It would be bizar to relate this swing to the specific form of mining going on at the time as it was all mostly GPU mining with similar ROI. Mining did not change significantly, but bitcoin price swung by an order of magnitude.
As i see it, ROI is completely dependant on price and is thus just another float on the sea of speculation.
You cannot predict ROI in the bitcoin ecosystem. It is just not stable enough.
So actually thinking about mining rig ROI in this economy is nonsense. You just don't know.
Funny thing is that most miners kept mining at $2. This means most miners were somehow losing money (extending the ROI faster than they could make up by selling their mined coins. Break even point is covering electricity costs (if extended to infinity the buying price of the rig becomes insignificant) so the price could not have gotten lower than the price you pay in electricity to mine one coin. Yet it did and people were still mining.
People were mining despite the fact that their rigs had ininite+ ROI.
Mining is therefore a speculative undertaking and has no simple direct relation to current price.
You need to take into account the miners expectation of future price.