If you think there is a chance that Bitcoin will continue gaining value long term: - Decide what you think a bitcoin could be worth in X years - Multiply that

If you think there is a chance that Bitcoin will continue gaining value long term: - Decide what you think a bitcoin could be worth in X years - Multiply that by the probability that outcome occurs - That's your 'fundamental' price Ex. if you think bitcoin has a 10% chance of being worth $100k in the future, it is rational to buy at prices up to $10K. (some time-value of money handwaviness, but can be a useful way to look at things. ideally should be compared against other investments)