I'd state what the parent comment says a bit differently: the availability of data for purchase does not make its purchase by law enforcement magically "reasonable".
> The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
In a digital world, one's "Person" and "effects" have become inseparable from the phones/platforms we communicate with. Participation in many cases is not a choice if one is to function in society.
The requirement that warrants are issued only upon establishment of probable cause also highlights the issue here. It seems highly dubious that a company holding your data and selling that data is somehow an acceptable end-around the warrant requirement.
Is this all technically legal? Seems like it might be. Is this what the authors of the 4th amendment had in mind? Seems extremely unlikely.