Ok sorry I see it has been already answered 
At current difficulty, on 20 nm process and 10 cents per kWh, I'd guess around 200, maybe a little less...
*edit*
"Is this even possible?"
No, not really. It's basically a feedback loop. unprofitable miners will turn off slowly and gradually the hashrate will follow the price, though there can be considerable lag.

Can somebody share with all of us, at what price level does BTC becomes unprofitable for the miners and they start shutting off they rigs and BTC collapses completely? Is this even possible?
At current difficulty, on 20 nm process and 10 cents per kWh, I'd guess around 200, maybe a little less...
*edit*
"Is this even possible?"
No, not really. It's basically a feedback loop. unprofitable miners will turn off slowly and gradually the hashrate will follow the price, though there can be considerable lag.
What about a more modern SHA256 altcoin? One which is more profitable to mine & most miners switch to to make money?