The argument "if you had bought bitcoin at the time Z" and comparing it to a different investment is a fallacy, as it comes with different risks and possible rewards.
Collider, let me help you think about this more clearly.
... bla bla bla ...
Obviously, if you don't care whether you recover your costs, then all this doesn't matter.
Just for the sake of my love to math (and this is the last post I will write in the subject of ROI):
Let's assume fixed BTC price for ease of math. We don't really know where it will be in 1 year.
In order for the SP30 to become non-profitable, it has to mine less then 100$ a month.
Today it would mine about 2000$ per month.
That means the difficulty rose by factor of 20.
That means that the network difficulty is around 2400PH, so someone have manufactured over 2300PH of miners.
Lets assume, for fun sake, that our competitor starts using today 16nm technology to make 10TH miners for 2000$ and he is building data-centers (let's say the data-centers are build for free, and there are no cooling expenses, because this competitor is a polar bear with his own construction company).
He will have to create ~230,000 of those 10TH miners and it will cost him (just the miners!) 460 million$. Let's assume the bear is taking a loan of 480M$ from the penguins for 5% annual interest.
And if SP30 6TH mines makes 100$ a month, this 10TH polar bear miner makes 180$ per month.
Let's assume electricity costs of 100$ per this miner (that covers DC IT, power etc` - really efficient bear that is) - this means each miner makes 80$ profit per month till autumn 2015, when we have the split. Each miner made ~1000$, didn't even ROI. Now miner makes just 90$ and doesn't cover the maintenance. Now the penguins are coming for the bear and saying like "Yo, bear, where is our dough?" and the bear is like "What are you talking about? That was other bear, guys, I am a tourist" and they are like "You have a T-shirt from the BTC conference, that is you, give us your private key". And he is like "I am sorry, I didn't compute the ROI of the 260,000 that I build, let's work out some deal" and they are like "no deal for you bear, get the f**k from Iceland"
Now I have to go to sleep, please upgrade to latest FW 1.4.8, the best FW for SP10 miner ever made.