people's desire to buy it. A ticket to a football game can be exchanged for goods and/or services.
Something is worth whatever the market will bear. Of course, the hackers would be prosecuted.

Now, is it a terrible investment? Yes. Just as stupid as tulips, or any number of other things that have bubbles. Whenever there's a purchase for an investment vehicle that is rarely used and is only going up because it's an investment vehicle, then you're going to see a crash.