BTC was created with a new transaction system without a central authority. The BTC can be used in the future as the main currency that we gonna pay with. But what's gonna be the value of a main currency? What's the value of dollars or eur?
-Answer is: The dollar IS the value. The dollar doesn't cost anything. The dollar is the value.
If BTC is gonna be used in future, it not gonna cost anything, because the BTC is gonna be the value. It not gonna be like Bitcoin cost 50,000dollars... Bitcoin not gonna cost anything because Bitcoin IS the value. But that's probably not gonna happen. We not gonna pay with BTC but with stable coins like USDT...
For now base on what we can see and believe, bitcoin is coming up to the standard of the US dollar in the nearest future whereby it will be generally acceptable and adopted as a legal tender, though I cant say it will erase the US dollars from existence but likely to work along with US dollars as the world most recognized currency, bitcoin already is the leading cryptocurrency and the value cannot be exactly predicted as its volatile but can place a great significance other than US dollars in the nearest future.