My question was: if you only use a computer for mining, and the profits from mining are decreasing all the time, how do you even know that you will be able to recover what you paid for it. It's a risky proposition. Which makes all the rig buying seem a little reckless, no?
Someone with a rig, tell me what the numbers are.
at this point it seem most new comer already missed the boat on the easy money...
its a function of how fast you can mine for BTC and the market exchange rate.... missed the boat on the $30/BTC rate, and the difficulty have gone up a few times so its much slower to generate coins now.
Is it worth it to mine with what you already have? probably yes, is it worth it to go spend a boat load of cash and build a dedicated mining rig? personally I say no.
If you use a credit card to buy your mining rigs, basically you get a 2 month free loan (unless you have 0% apr) to recoup the cost before you have to outlay any cash. Maybe worth it to upgrade an existing PC, if you can get the 5830 for $110 that would fit under this model @ $15/BTC current rate.