It also has to offset benefits received from other programs like welfare, unemployment to help cover the cost.
IMO $700 / month is about the right number where it helps with basic needs and dry spells but isn’t so much that you’re incentivized to withdraw from the job market entirely.
At the same time, minimum wage can go away entirely if UBI is in place since the UBI doesn’t go away like unemployment the moment you have a paycheck. You work to earn more, not trade income sources.