It can function at any price. There is no price too low. The only extreme possibility would be a temporary denial of service if hashrate dropped too quickly, c

It can function at any price. There is no price too low. The only extreme possibility would be a temporary denial of service if hashrate dropped too quickly, causing blocks to come extremely slowly until the network adjusted to match the current hashrate, resetting block time back to the target. In such an extreme scenario, this could effectively pause commerce for months if nobody helped bring the hashrate back up until the adjustment. There are many mitigations possible: 1. The remaining miners have newfound control of the network so could push in a difficulty adjustment algorithm change to something more modern and adaptive, restoring service immediately. This has been done on so many other smaller networks that it isnt experimental. 2. The remaining miners could do other things too like a one time sooner difficulty adjustment There are a few networks experiencing this right now and addressing it in different ways. There are always a few real money cryptocurrency networks going through these growing pains so we can see all theoretical experiments happen extremely fast.