Bitcoin is dead when the flow of new fiat to the exchanges stops. That is easy for the exchanges to measure but hard for most people. It doesn't seem to be a published quantity.

Sure you can claim that it's not dead even then. Surely, people could be trading goods for bitcoins among themselves in the absence of fiat/exchanges. Dismantling of exchanges does not directly cause (or logically imply) a lack of desire to trade.

However, since the OP specified BTC Price, it is foolhardy to dismiss the correlation. Fiat exchanges were created in anticipation of supporting those who wanted to trade without mining bitcoin. Without desire from those folks, BTC price has no meaning. Exchanges become merely pari-mutuel wagering facilities taking a rake until there are no more rakes left to take.