What? That's no way to 'disprove' a bubble. Of course the people buying stuff thought it was valuable, or that there would be a greater fool to sell it to. That doesn't mean they were right.
Although it’s true that the most expensive tulips of all cost around 5,000 guilders (the price of a well-appointed house)...
How is that not irrational? Come on.
I was able to identify only 37 people who spent more than 300 guilders on bulbs
Is this evidence of absence, or absence of evidence?
Anyone who had both bought and sold a tulip on paper since the summer of 1636 had lost nothing.
Well, yes. It's the bagholders that lose out in a bubble. If you manage to buy and sell something that's overpriced, then you'll be ok. But someone will be left holding it.
In any case, the south sea bubble is a far far better fit for bitcoin and crypto coin mania. They even had comparable ICO sales!