The Kingdom of God is within you, it like the Pearl of Great Value is hidden yet present. Like the Pearl of Great Value one must sell all to obtain the Kingdom.
This selling all is indicating the cost, which is the loss of ones reasoning, or perspectives of life, and of God, all for the gain of knowing God and His righteousness in a one to One relationship, one that God establishes and interacts with one by Faith.
This is the whole purpose of ones existence to discover and enter Gods realm of Life. And nothing can compare to what God offers one, Salvation and True Peace of mind.
Like the Pearl of Great Value the Kingdom must be uncovered to be obtained, yet once obtained it’s Great Value never is lost and only gains for all eternity and beyond.