actually i'm running an older Nvida gpu and so I get lower mining rates with that but it is what I already have. I have it over clocked to the max of it's ability to remain stable and not overheat the rest of the system. I actually purchased a 5gh Asic and figure with the delivery delay I have enough time to figure out what the heck is going on. (hardware geek i understood the overclocking and the difference with the nvida part right away) then it will pay for it's self after a little while purchase another etc. dont forget the market will stabilize the prices to the point that will replace the decrease in the rewards to the point that your net gain in fiat will be consistent over time resulting in the same cash now then and before. or are there some mistakes to my logic.
Now I have a question for you. Someone tolled me that if I overclock my cards I need to increase the voltage. Even if that is not necessary for stability. You just need to or you will damaged it. Is that right? It sounds wrong to me but I'm no expert...
And if 5gh is BFL you will probably wait a long time. When did you order it? You will probably wait to the point that it will take some time to pay it self. It might even used more electricity then it will give out.
About your logic. There is over 50% of bitcoins already mined so there is no guarantee that the prices will cover cost of mining. There are people that have a lot of BTC and if they sell them the price will drop. It is always a risk. Price will get stabilized as soon as there is a big enough market that uses BTC and doesn't convert price according to $/BTC or /BTC or something. But then again I might be wrong...