What if all cryptocurrencies merged together? Cuz if it merges, then the price of Bitcoin would pass $100,000? The market cap would be at $3 trillion dollars but what will the price be for 1 coin?
The price for 1BTC is always 1BTC. It only depends on how much someone is selling 1BTC at for a certain fiat value.
Altcoins exist to prove the difference of opinion among people, they are not agreeing on everything that bitcoin has to offer but they want their own coin to fill the gaps. Therefore altcoins exist.
What you say, like merging them all, is technically and ideologically not possible, but their combined fiat value can be calculated. Such changes would not be occurring all of a sudden either.