That's exactly what UBI should be: Enough to remove the desperation of "subsistence" from the obligations the individual must fund with their labor.
A drowning man will trade the lives of his wife and kids for one more breath of air; nobody can hope to earn a living wage while competing for work against a drowning man. It's only when he can keep his own head above water that he is able to consider anyone else. A UBI that barely keeps his nose above the waterline is good enough, and infinitely better than what we currently have.