OP these are your basic factors ranked in order of how they affect bottom line:
- Initial investment in equipment cost
Day you can start mining
DIFFICULTY on that day
Estimated difficulty increase based on historical data http://mining.thegenesisblock.com/
Electricity cost (which is negligible in most cases for BTC but absolutely necessary for scrypt)
As the value of BTC goes up the cost of currently available equipment goes up.
In your scenario, you could spend 13k on a 312ghs miner starting
TODAY. And make your cost back by the end of January.
Then you could
sell your 13k miner for roughly what you have in it (unless btc tanks) and have
24k total profit.
To get the same with investing, you'd have to buy ~13 btc today and hope they
double to $2000 USD by the end of Jan.
(This investing in BTC thing was great when you could get 60 for 13k, but it's not as glamorous when you can only get 13btc.
The
PROBLEM happens when you spend 13k to get a
312ghs miner in Late January or early
Feb.
Starting January, you'd only make half your investment back.
Starting february, you'd only make $3k of your original 13k back!
Of course, once you sell the equipment, you can break even or come out a couple of BTC ahead. But this
particular scenario you posit is a bad one.
With an 1800w miner that cost 13k, you'd need to start off mining at 550GHS in January, or 1100ghs in February to even BREAK EVEN in 2014.
One thing to note that's not on this list is the value of the BTC. I like to estimate their increase in my calculations. Other's aboslutely do not do that because it's so speculative. For you I have left that part out.