good plan, but sadly it will never come true. bitcoin, ethereum and bnb will never reach the price you set. because before that happened the price had gone up. You will only regret thinking like this. This is already at the lowest limit and for the future there will only be an increase.
Yes, it is indeed very difficult to determine the price of each cryptocurrency because all cryptocurrencies always have a price that fluctuates except for stablecoins, and also note that the crypto space is not to fulfill everyone's desires.