In theory, the current price should be the probability-weighted-average of future scenarios, discounted to the present with discount-rate.
In the very beginning of Bitcoin, we wonder how "nobody" realized that it could become a million times more valuable in 5 years? Why did sirius sell 5kBTC for $5?
A few answers:
- information not spread
- buying additional coins does not give a real-life edge (if you are broke and in a small probability make $20M instead of $10M not a big deal for most)
- discount rate is high, making a large payoff in the possible distant future be of little value now
- time sink/stress generator - many don't want to invest until it is big since while it is much less upside, it is also easier and safer (I refused to order a promising free energy device just because of the hassle. I can order it a few months later).
In practice, there was a time when log-linear trendline was the best fit to the data. Currently not too sure about it.
There is a diminishing return on profits when a large enough market cap is reached. But this means diminished risk of losses as well. If BTC reaches the $100 trillion cap which is required for it to dethrone fiat, the diminishing upside kicks in starting at 10,000 times higher price than current. Clearly this is still a better investment than most re:upside.