I disagree with this view. I don't think there is a bottom line for cryptocurrencies. Many people say that mining prices are the bottom line, but I don't believe it, because when bitcoin falls quickly, miners will choose to stop mining instead of buying bitcoins!
Yeah you are right just as nobody knows the top price of bitcoin; nobody knows the bottom price of bitcoin too. Price depends upon the investment capital; if the demand for bitcoin increases and people put their money in bitcoin the price will go up and if people do not invest in bitcoin the price will automatically drop because of no or very less demand.