Well the good news is that once UBI is implemented all future elections will boil down to politicians promising a bigger UBI increase than the other guy. Problem solved!
The numbers are similar for other western economies.
Okay...
> ... add extra money from increased taxes (make it flat 50-60%)
No. You can't presume anything about increased revenue from extra taxes. If you taxed income for any amount of work at 50% and you give every "household" 42,000€ (which I assume is livable in NL) you would drastically reduce the incentive to work and pay taxes, so your actual tax revenue goes down.
> The numbers are similar for other western economies.
The numbers generally say that if you pool all the social spending, you can redistribute it to everyone and it will pay for a subsistence level of living. However, a big part of that pool is pensions, which are liabilities in proportion to the amount paid by the individual. A lot of pensioners would be subsidizing people who never paid into the system. That's the main problem.
Good luck passing a bill that raises my effective tax rate from 17% to 55%. Obviously if you take a whole lot more money from everyone else there will be more to hand out to others.
Also remember you counted in pensions into your budget, those are separate from taxes. So the net profit from working would be maybe 30% or less - ridiculous!
That is already about $21k per year per household.
If income tax was raised to 50% flat and you keep all the social security and single payer spending, your paycheck would net maybe 25% of your salary. Who works full time for 25 cents on the dollar when they can just retire?
So then people won't work full time, your tax revenue, your single payer money, your pension money, it all goes down. It can't pay for your UBI.
Even worse, all this spending you are talking about redistributing isn't even paid for today. It's funded by debt. With the boomers retiring, there are huge amounts of unfunded liabilities.
It may not be obvious to you, but what you are proposing is that we can just all sit back, work less, print money and everyone will be better off. It's a fantasy.
To be clear, I support a UBI, but one has to be very careful about the actual amount.
And limits/process on how/if it can be raised. Otherwise, it's likely to devolve into people literally voting themselves an ever-increasing share of money from the treasury...
If I'm to support UBI it would be a meager existence: enough that you can eat. Like socialism UBI need to account for eventually somebody needs to do something. Food needs to come from someplace, that means somebody had to work for it, and that somebody should get some reward for it.
And of course, $600/mo/adult is an extremely meager existence.