Now, people have UBI. Let's say, 1000? Prices now reflect the poorest person with 10+1000 and the richest with 10^1000+1000. Goods and services that targeted the 10 income market are now priced for the 10+1000. Housing goes up, food goes up, everything goes up.
The power of money is relative. Adding money to an economy adds inflation, and adding money até the base of the pyramid inflates crucial goods and services.
So, unfortunately, the solution isn't as simple as UBI.