Today 1 bitcoin is $425, but by the end of the year it may grow up to $1000 or fall to $100. Everyone who INVESTs in bitcoin needs to understand the risk, but we expect the real growth! Even if the bitcoin will stay at the same rate you'll get value paid in $ in 2.5-3 month back and since this point you start only mining (earning) bitcoins. Nobody can predict the value of bitcoin in 24-36 months, but what if this will increase 10 times?