A Universal Basic Income is not necessarily paid to everyone, at least not directly. A UBI means a certain income level is guaranteed, if you are earning more than the guaranteed level, you may not be given anything in addition. This is most clearly demonstrated by one proposed implementation of UBI, namely, a negative income tax. A negative income tax would entail those earning below the guaranteed level being paid enough to raise their income to the guaranteed level. Those earning more than the guaranteed level are taxed.

Negative Income Tax is pretty much the only implementation of UBI I personally could get behind. I just wouldn't be able to support an implementation of a UBI that pays Bill Gates the same amount as a person born with a severe disability (which obviously they had no choice about being born with).