1 GH/s currently costs about 0.046 BTC, but it will never mine that much. People buy it anyway ...
I can't believe that thousands of people, particularly people who are tech savvy enough to get into bitcoins in the first place, would just knowingly buy mining power at a loss. The only conclusion I come to is that they treat the GH/s more as a lease. They use it to mine for a few months knowing they will sell it back (maybe for a gain or maybe for a loss). So you make a profit by combining the btc amount you mined along with the sale price of the GH/s and hope that it came out to something more than what you spent initially. And then of course you have to hope that the exchange rate of bitcoin didn't go down while you mined as well. That is the only way I can understand why people buy GHS at these prices.The price goes up and down but in general it falls as much as the difficulty rises, so you cannot expect to make a profit from trading either, although some people do.
