So if you set UBI at (say) $20,000 a year net of any taxation every million people you pay it to will cost $20 billion.
Let's say that 65% of the population is over 18 and therefore eligible for Basic.
NZ population approx 4.5 million so that makes 2.9 million or thereabouts.
So we need around $60 billion a year to cover that. According to the Treasury that is about $10b more than was spent last year on Social Security & Welfare, Health and Education combined. Total core Crown revenue for the same period was $71 billion.
It won't be cheap, will it?!