You need to use the correct word if that's what you meant.. You're confusing the word "stable" with the word "valuable"..
Stability is what Bitcoin needs to make it useful for that exchange. It doesn't matter what it's price is, as long as it's relatively stable, but if you exchange USD or gold for bitcoin to buy something that is roughly $10 USD, but by the time you go to purchase it, the bitcoin price has changed enough that you can't afford it and need to try again, then it's not useful for exchange.. Satoshi Nakamoto has made it clear a number of times, that he believes that the stability is far more important.. Instability always has the potential to help you out as much as it hurts you, but you need to know what to expect when you're using something as a currency, which is was Bitcoin was always intended to be. No one ever thought you could use Bitcoin to coat electrical contacts with it to prevent corrosion, but that works great with gold. ..so if you're talking stability (and you're speaking English) then when you try to say that gold is stable, you'd be mostly correct in thousands of years of history (room for different opinions there), but it certainly wouldn't be correct when looking at the last couple of years.. For Bitcoin's lifetime, bitcoin has been just about as stable as gold (not quite, but if you could get rid of July 2011, you'd be pretty close).
As far as what they cost to produce as compared to their actual value: Bitcoin is designed to allow an equilibrium to be met that always keeps those right about the same, and that will always be the case. People (not even Bitcoin miners) don't leave money on the table for no reason, and they don't throw it away either.. It will always cost about 1 bitcoin to produce 1 bitcoin. Gold is exactly the same way.. Right now, the ratio is off a bit (in the miner's favor), but that will balance out soon enough when either the gold bubble pops, or more people enter the gold mining market. It just takes a little longer in the non-virtual world.