We're officially launching UBI

In order for it to be there for the people who need it, it also has to be there for the people who don't want it. Right now, most people in the US live in homes far bigger than they need, but we also have people who have no homes at all, and those who pay rent far higher than their home is worth. If everybody has a guaranteed space to occupy, though it be meager, then rents for more luxurious and prestigious digs will not include the cost of human misery, from a combination of those people who fear not having shelter and an intentional dearth of supply because that fear may be monetized.

If everyone has their own monastic cell, no one can inflate the price of their own freestanding home by being such a NIMBY that no new housing can be built. There will be enough housing, by public mandate and eminent domain, even if no luxury housing is available.

You know an easy way to produce a lot of bottled water? Use bigger bottles, and reuse them. Stamp out a bunch of stainless steel 20 L watertight containers, let's say two for every person you wish to serve, so that they have one to use while the other is being refilled, heat-sterilize them, and fill them each with 20L of tap water.

For 1000 people, you make 2000 bottles, and sterilize and refill an average of 100 per day. At the end of the year, you have produced 730 kL of bottled water, with only 40 kL of actual bottle volume. People will still demand disposable 0.5 L plastic bottles for their convenience, but they will have to pay for them, and it would definitely not be at the tap-water rates of ~$0.25 per 20 L. The value of the drinking water benefit would come from the bulk treated-water rate, because nobody needs to drink out of tiny disposable plastic bottles; they just need water at the minimum standard of purity, at the cheapest price.

It is true that there would be no cash price available for a filled 20L steel bottle, but you can still price it by adding up the costs of production. Those are not made from things that are free. So you have the wages of the programmers and machine operators for the stamping and welding robots, and the steam-cleaning robot, and the refill robot, and the delivery truck, and the truck-to-doorstep robot, and the capital expense of building them, and the operating expense of running them. Then you add 7% as ownership incentive, and that's the nominal cost. You just have to show receipts and pay stubs instead of counting up the gross revenue and dividing by number of units delivered.

It would be a workable system, provided the additional complexity is largely automated. It would be far simpler to do it via public agency and just skip all the tax calculations, but US people are more wary of communism and corruption than they are of public-private partnerships, for some strange reason.

UBI isn't intended to solve economic problems that existed or even could be centuries ago - it tackles the problem of poverty of people becoming unemployable due to technological progress, despite very high productivity allowing to satisfy the basic needs of everyone with a small fraction of gross national product, or a small fraction of population working on those basic needs. It's a serious problem for the future, but we're just barely (and only in select locations) beginning to have it. UBI doesn't make sense until the abovementioned conditions arrive, but they're coming, and I'm not aware of any other sensible solutions for these solutions.

When this situation comes, the good option is that the society simply gives the new class of unemployable people their basic needs one way (like UBI) or another; the evil option is that the society doesn't give them the basic needs and they starve (since their labor has no value and they have nothing to trade for these basic needs); and the third option is that they take the basic needs in a revolution that likely destroys half of the society. Really, noone wants the second or third options, including most of the 0.1%, so we will see some mass redistribution system being implemented.

In 1917, taking all the resources from rich people and giving it to poor people wasn't enough to keep the poor people out of starvation for long and destroyed the productivity totally. In 2017, taking more money from the rich to feed the poor doesn't require even close to taking all their resources, as feeding the poor is so much cheaper compared to 1917; it would be deeply unpopular but is doable without killing the rich, and the society could sustain such level of taxation indefinitely if they wished even if nothing changed - but it's going to change, and in 2037 taking enough resources from the rich (i.e. the owners of highly automated means of production) to feed everyone UBI-style would be expected to be just a minor tax, and a boost for the economy, giving spending power to people who'd otherwise have no spending power at all.

Most (all current?) welfare schemes have a disincentive for work because earning income disqualifies you from welfare, and getting a poor job can make you worse off even if the welfare amount is below the minimum wage, since going to that job often also does add extra expense (transportation, caretaker for kids and other dependents, etc).

With unconditional basic income, however, all the job income is extra, which is a big difference in motivation especially for people who can't hold a full-time job because of health issues or having to take care of others.

Furthermore, standard welfare systems don't handle structural unemployment well - they don't provide a long-term (decades, not months or years) means of support to able-bodied people that can't get a job. Historically, that wasn't much of a problem - able-bodied people could get a job if they really wanted most of the time; if there was an economic slump, then it went away in a couple years (and welfare could help ride it over), and if they couldn't get a job, then retraining was a solution. In the future, the situation is different, we should expect millions of people, eventually a majority of population, whose labor is economically unnecessary (it can be done by machines better if these people aren't allowed to participate) despite any reasonable retraining. This issue is(will be) new, and current methods clearly won't work.

People respond to "carrots and sticks", and UBI brings a much more sensible set of "carrots and sticks" than progressive taxation + classic welfare.

A negative income tax fits the USA process where most people have an annual activity of filing their income taxes and getting a check for a difference that they're due.

That's not how it works in most places around the world (USA usually is the exception rather than a reflection of common practice) - in a much more common approach, the common worker has zero personal interaction with taxes, if an income tax exits, it's withheld by the employer; and only a minority (e.g. businessmen) would have some sort of tax declaration. In such systems, implementing a negative income tax is much harder, since the current taxation mechanism doesn't provide any system for interacting with these people whatsoever, and simply paying an amount receivable upon showing their ID is comparably much simpler and cheaper to implement.

Regarding your first paragraph: Agreed.

Regarding your second paragraph: You're looking at this as a measurable global issue that will happen at a single time resolvable by a single government entity, but that's not how it will unfold.

It won't happen overnight, so there will be no point for those options to be evaluated. Let me pitch you (what I see as) a more realistic option:

Some countries will try to implement UBI. They will encounter the same problems opponents have been warning about. The productive will (over time) move to countries that don't take so much of their wealth. The people receiving more than they're contributing will have more children, will have more votes, and will vote to take more and more from the decreasing minority. Even if you can make food truly post-scarcity, housing, healthcare, and other goods/services are not.

If everything is truly post-scarcity: It'll be no problem. Those countries won't really need the wealthy. But I'm not sure true post-scarcity actually exists, and I think (especially in the US) UBI would be a moving target that only ever goes in one direction.

You're right, though, that I don't really have a solution if (e.g.) 80% of people no longer have a meaningful way to contribute to society. That may be fundamentally impossible to solve. But that may never happen and we may never have true post-scarcity, so we shouldn't be redesigning society based on the premise that wealthy people are an endless money tree, and if it's wrong, society collapses.