People could be selling for under 1 because they see a better investment elsewhere... BTC-Mining probably won't get their equipment for a while if they haven't ordered it yet. By the time they get it, what was once worth 1 BTC of ASIC hardware could be worth less than .8 BTC
They will not be paying the same amount in BTC if they hardware buy in the future. The left over will be reinvested into more hardware, thus the share price will remain the same or grow. If this left over is stolen or fraudulently used while the price stagnates, well, then we are going to have a problem.
This isn't a fixed megahash bond.