But supply cannot reach 0. First of all, it will take decades before we reach 21 million, so you don't have to worry about it running out. Maybe your children will face this problem if Bitcoin exists in their age. As long as there are buyers there will be sellers. For every price level there's a seller. They're here now at 30k and there will be some at 300k USD.

How do you price abstract items like art? How do you price domains?
There are always buyers willing to pay what they feel is right. What for you could be worth $100, for someone else will be priceless. I don't see a problem here.