When was the last time the world saw an entirely new asset class come into existence?

Most financial assets are introduced at a price that is believed to be pretty accurate.  The asset price can be a bit volatile initially during price discovery, and then the price only moves as the perceived value of the asset changes.

Consider the fact that Bitcoin was introduced at a price of $0, that the value of the smallest unit is currently only $0.00016 per unit, and the possibility that so few people are engaged with the asset that it may still be in a price discovery phase.  Is it not possible that at the end of the price discovery phase, bitcoin may be sitting at a relatively stable price of $0.001 per smallest unit ($100,000 per BTC), or $0.01 per smallest unit ($1,000,000 per BTC), or any other price that is significantly higher than the current price.

If the world is only just now really taking notice of this asset, and if it is significantly under-priced to start with, then wouldn't you expect the price to run up VERY fast?  It is likely that it will overshoot, and that will be followed by a significant drop in price, but that could be a drop from $1.5 million per BTC to $1 million per BTC.  I'd expect some significant oscillations over the next 5 to 10 years.  However, a large and fast increase is not necessarily an indication of a "bubble".

I'm not saying it isn't a bubble. I'm just saying it's difficult to know for certain, and that there are other good explanations for the recent price behavior.

Finally, note...  Bitcoin hasn't been $2000 since July 17.  While that isn't very long ago, I'd say that 21 weeks is a bit more than "a few".