That chart is with a
full bias towards them, on a best case scenario where they have 350TH mining in December from just the initial 2M sold shares, the chips turn out as good as expected and there is no more mining competition than what's been already increasing the past months, from the current hardware suppliers.
You can simulate easily other scenarios:
http://mining.thegenesisblock.com/
Until forever? It's only going up from those 75%. Those are only based on the hashrate added on the last 30 days.
It's far, far from "full bias towards" BTCGarden. I have doubts in their operations, but you aren't giving the right amount of optimism to say that.
1. 30 days is quite an arbitrary time period.If you take March 2013 - August 2013, the difficulty increased by a factor of 10, which averages to ~58% per month, in which case there's a >30% profit in the first year.
2. An increase in BTC price could increase profit dramaticallyThis is true when we assume our difficulty projections are accurate. They then have a higher profit margin, and that increase is always more than the effect of the growth of BTC itself.
Say originally $100 earns
BTC1. That's about a 5% profit margin by the current Mt.Gox price. But BTC is then raised by 100% to $210; the profit margin becomes 110%, which is actually nearly 22-fold.
For a stock that is valued by its profits, this factor shouldn't be overlooked.