So your premise is that all drug laws should be abolished/not enforced. Sorry but I only partially agree. Certain drug laws, marijuana for example, are overreaching. Other drugs do cause harm to society.
If the laws prohibiting those drugs actually made them unavailable to would-be users, then and only then would I see your point. They're failing to do so, have always failed, and will continue to fail for the foreseeable future. These are simply facts and these facts are not controversial at all. As I said, even in the highly secured, scrutinized, searched, regimented environment of a prison, where all the variables favor the people trying to prevent drug use, not even in those places can we keep drugs out. One way or another, they continue to be smuggled in.
What these drug laws are accomplishing is the enrichment of violent gangs/cartels, for whom the illicit status of drugs means far greater profits. Even the occasional large drug bust just amounts to less competition, and it's generally not the big kingpins who are bearing the risk. What the prohibition laws also accomplished is the steady buildup of a police state and the erosion of the 4th Amendment. The asset forfeiture laws alone are an abomination in any country that even pretends to be a free society. All of this is caused by trying to enforce an unenforcable law. It's the only outcome that can be expected from trying to do so.
I agree but some drug consequences are not confined to consenting adults. Some drugs cause people to be unable to hold jobs, cause them to commit crimes to support their habit, etc. I realize that alcohol does similar things but to a much lesser extent. The percentage of productive crackheads is much less than the percentage of productive alcohol use. The consequences of this drug use is spread to the rest of society in welfare costs, health costs, insurance costs, policing costs, etc.
Again if the prohibition were actually capable of stopping the drug use, this would be a legitimate concern. The policing costs could be eliminated entirely. Legal drugs would cost far less per dose, removing much of the incentive for addicts to rob and steal from others, reducing crime. Hell, state governments could give away free drugs to addicts and it would cost less than what we're doing now, both monetarily and socially. The reason productive crackheads are less common than productive alcoholics is that the alcoholic can easily purchase his drug anywhere and can afford it since it's legal and cheap. The other costs you mention like welfare, health, and insurance are effectively fixed costs, because right now anyone who really wants drugs can get them.
The best way to reduce the harm caused by irresponsible drug use is to treat it as a public health issue, not a law-enforcement issue.
The issue is around the word "unreasonable" which can be interpreted differently by different people. What is unreasonable to one person may be reasonable to another. Too many people seem to interpret this an "any search without a warrant" but that is not what the Constitution says.
Indeed, unfortunately that isn't what the Constitution says, but it would be wonderful if we actually had a pro-freedom Supreme Court to make such a ruling. These days the Court is little more than a mouthpiece articulating bullshit justifications for what the police are going to do anyway in order to create the appearance of legitimacy. Also, if drugs were legal and regulated, the incentive for the vast majority of police searches would disappear, as the vast, vast majority of prisoners got there because of drug charges. Then most searches would be for important things like murder weapons, not for unimportant and futile things like trying and failing to tell adult people how to live.