If you give everyone $1000 a month (to round the numbers) now the work of someone who makes $1200 a month is only worth $200 (as one can make $1000 just by idling). Would this person want to work for $200 a month?

This is a major disincentive of work.

So what? If the person has no reason to work, then they shouldn't. Humans are entrepreneurial by nature. Everybody has crazy dreams that have long forgotten because they needed to eat. I don't even want UBI so people don't starve, I'd like UBI so people can live comfortably without having to work. Everybody should feel "rich", the same way most silicon valley kids do/are.

You made an emotional argument that seems angry at a certain group ("Silicon Valley kids").

However, the work that will not be done by those people who can do it but don't want to will still need to be done. The solution will then be to hire people at higher wages.

But since these higher wages are not a result of increased productivity, the employers won't be able to sell more. The result is that prices will go up, generating price inflation. And we know inflation is the worst of all taxes, as it affects the poorest the most.

In the long run, the money received via BI won't be able to sustain the "comfortable living" that it was supposed to.

That's not how basic income is supposed to work. The person who worked would get $1000 basic income PLUS their $1200 wages = $2400.

Sure, above a certain level people's taxes would go up, so they pay back some of their basic income as tax. But that wouldn't kick in until people are earning rather more than $1200 a month.

Ignoring the magical thinking aspect of this (where will this money come from), this assumes that people will still want to work after receiving basic income.

This also has the inflationary consequences that I mentioned in another comment: you're effectively increasing wages without increasing productivity. This will cause prices to rise because employers will face higher taxes so that the state can support basic income, and demand will rise because people will have more money.

This will cause inflation, and in the long run purchase power will not increase, while society will be worse off with less people doing productive work.

Do you really think most people would prefer being poor to working and thus not being poor? Look at all the lengths people will go to to get money. Most people really, really, really like having money, and that doesn't stop just because they get a little bit of it.

Sure, some people won't work. But most of those would be people who either would have a hard time finding work, or who have some specific other thing they'd rather be doing.

Some people are not going to extra lengths to get more money now. Those people might be happy with their current income, however low it is. These people will prefer to stop working.

You are also confusing money with wealth. Basic income may give people more of the first, but its inflationary nature does nothing for the second.

UBI should be paid irrespective of other income. So that person earns 1200 and finishes the month with 2200.

What tasks do you consider "work"?

Child care? Elder care? Volunteering?

I think what you're trying to say is something like "people won't work anymore but they will be able to stay home and take care of their elders". Which I think is a valid point, but also one that is only true for a really small minority of the population, certainly not enough to justify putting the whole population on welfare.

Consider this scenario: you're taking care of you elders and you need to go out and buy some medicine. But the drugstores have all closed, since nobody wants to work there anymore (why would they? They're at home taking care of their elders too). Do you think this is not a realistic scenario in the long run? Why not?

Whilst some may be happy to survive on their low basic income, most will be motivated to work to achieve a higher standard of living.