“Very often the things that cost nothing cost us the most heavily; I can show you many objects the quest and acquisition of which have wrested freedom from our hands.”

Source: Systems Engineering Tools, (1965), Systems Engineering Methods (1967), p. 13

From Declaration of the Causes and Necessity of Taking Up Arms https://en.wikisource.org/wiki/Declaration_of_the_Causes_and_Necessity_of_Taking_Up_Arms, adopted by the Second Continental Congress (1775)

Variant translation: Liberal institutions straightway cease from being liberal the moment they are soundly established: once this is attained no more grievous and more thorough enemies of freedom exist than liberal institutions.
Expeditions of an Untimely Man, 38
Twilight of the Idols (1888)
Context: My conception of freedom. — The value of a thing sometimes does not lie in that which one attains by it, but in what one pays for it — what it costs us. I give an example. Liberal institutions cease to be liberal as soon as they are attained: later on, there are no worse and no more thorough injurers of freedom than liberal institutions. One knows, indeed, what their ways bring: they undermine the will to power; they level mountain and valley, and call that morality; they make men small, cowardly, and hedonistic [genüsslich] — every time it is the herd animal that triumphs with them. Liberalism: in other words, herd-animalization...

Source: The Hunter

Some Men are More Perfect Than Others (1973)

Variant: When you have to kill a man, it costs nothing to be polite.