>no reason whatsoever why it couldn’t hit $1M, $1B, or go back to $1
Not entirely true. The value is driven by number of people invested x average amount they have invested. Most of the historic increase has been as the number of people involved increased. Currently that's probably in the 100 - 200 million people range. It could 10x from here to $1M per bitcoin but is unlikely to go to $1B or $1.