It is irrational because you think the price is too expensive, but based on technical analysis, ethereum price chart can touch $100k, it's just that the value will occur if the price of bitcoin is able to touch $1 million, if bitcoin has not touched the price of $ 1 million it will be very difficult for ethereum touched $100k.
why not maybe actually that is a fundamental question, but in crypto the possibility could happen but is determined by other calculations. because this is a question about ethereum, it can be juxtaposed with bitcoin, which is intertwined with the two coins.
if bitcoin increases, ethereum will do the same.
so if ethereum is expected to increase to $ 100K then it is certain that bitcoin must first reach a value which is probably very fantastic, it could be 25x the price of ethereum. now is it possible that bitcoin can achieve it, if it doesn't work it's also likely that ethereum won't be able to.