When people say, "what is a bitcoin worth", my answer is "try making one" then you'll know!
You can also try putting numbers into this...
http://www.bitcoinx.com/profit/ and see how much they cost to generate!
It assumes a BFL 50 GH/s Bitcoin Miner $2,499 @ 100w which currently has a 198 day break-even if BTC was $300.
Of course that assumes you have one mining today, which of course you won't, there's a looooong lead time until delivery!