I would note that prices are markovian. So if something doubles over night it means something happened to affect that price. All the information about the thing

I would note that prices are markovian. So if something doubles over night it means something happened to affect that price. All the information about the thing and its history is represented in the current price. Having that price double overnight conveys information that something is happening. It doesn't matter that the thing cost even more 10 years ago. You have to look at prices on the margin.