This is one more thing I don't get. I also read about it in group buys. They say: "when our group miners are no longer profitable we sell them and share the money". But who is going to buy non-profitable miners?
Here ya go. People are always buying non-profitable miners... I have no idea why.
If you buy with USD you have hope you make profit if Bitcoin price rise. And it seems it is hard to understand how the difficulty works and how quickly you can mine much less / day