I have serious trouble believing UBI provides enough to solve the poorest peoples problems without needlessly costing a huge amount funding well off peoples hobbies.

You'll still need affordable housing, you'll still need food programs, etc. I don't see how you save on cutting those programs.

Ballpark numbers: About 1/3 of Americans get government assistance, and typical administrative costs are 1-10% of the program.

Making these benefits universal would require spending 200% more, and save at most 10% in overhead.

Thus, optimistically, you'd be spending +190% more.