The thing about UBI is that it's universal. A 5% cut won't amount to anything useful. Looking at 60k a year average income a 5% will only amount to 3k a year. The actual number you're looking at is more like 20% cut across the board, regardless of income so you can get 12k a year. Next there's the issue of how that money actually makes it through and managing it all which is going to increase the cost further. Looking at the US you're effectively going to need to convince 2/5 to give at least 0.2 * income - UBI which isn't extremely likely. Assuming that the price of items drops at the same rate as automation takes over that 20% can stay constant. If for whatever reason that doesn't happen that 20% will keep increasing to account for that difference.