What is the test for exercise of the police power to regulate prices?

The court recognized in Munn v. Illinois, supra, 94 U.S. 113, that it is necessary to understand the principles underlying exercise of the police power in order to determine when the power is exercised in a constitutionally permissible manner, and explained that when property is affected with a public interest the property is no longer wholly private. "When, therefore, one devotes his property to a use in which the public has an interest, he in effect, grants to the public an interest in that use, and must submit to be controlled by the public for the common good, to the extent of the interest he has thus created. He may withdraw his grant by discontinuing the use; but, so long as he maintains the use, he must submit to the control." (Id. at p. 126.)

The court addressed exercise of the police power to regulate prices again in Nebbia v. New York (1934) 291 U.S. 502, 525, 54 S.Ct. 505, 78 L.Ed. 940: "The Fifth Amendment, in the field of federal activity, and the Fourteenth, as respects state action, do not prohibit governmental regulation for the public welfare. They merely condition the exertion of the admitted power, by securing that the end shall be accomplished by methods consistent with due process. And the guaranty of due process, as has often been held, demands only that the law shall not be unreasonable, arbitrary or capricious, and that the means selected shall have a real and substantial relation to the object sought to be attained.... [p] ... [p] The court has repeatedly sustained curtailment of enjoyment of private property, in the public interest. The owner's rights may be subordinated to the needs of other private owners whose pursuits are vital to the paramount interest of the community." (Fns.omitted.)