the value of bitcoin determined by the number of people and investor wants to become a huge value or low prices it depends on the users of bitcoin.
you are right, although we cannot predicted the exact price when it's increase or decrease, we could still use the price to buy and sell the bitcoin and we can make a huge profit. when there are too many wants to buy bitcoin, this will make the price moving so fast to be filled in the market and the price will moving up and down but this will not stay too long and there is a moment for the price to stay at one price level.