Why does bitcoin at $25,000 mean the end of the banks? You don't offer any reason for that statement.
For bitcoin to reach that level you have to believe that bitcoin is an investment, an asset class...like gold or stocks. Do you know what the highest price stock is? (Price per share). Berkshire Hathaway (BRKA, the A shares). The "A shares" of Berkshire Hathaway trade at $254,000 PER SHARE. And guess what, the banks are still here.
My point is that the value of an asset class has zero influence on the existence of some unrelated business. People still need banks. If the price of bitcoin goes to $25,000 it does not mean that everyone will be using bitcoin. There are nearly 7 billion people in the world and only 21 million bitcoin that will ever be mined (100 years from now). Bitcoin can very well be a rich asset class that exists along side so many others and at some point will be out of reach for the common person (to own a whole coin that is).