That's literally exactly what the GP post explains. If the funds distributed as UBI are the funds redirected from replaced programs, the costs are, by definition, the same.
> That would only happen if by luck the same number of people applied to basic income as previously applied for means-tested benefits.
No, it wouldn't. You are assuming equal per beneficiary per time period total benefit + administrative costs.
> Also, even if you have some new funding source, the system would have potentially huge liabilities if lots of people decide to sign up for it.
No, its not dependent on people who "decide to sign up for" since, by definition, an unconditional income is given unconditionally to every member of the target population; that's part of the basic calculation of the benefit that can be given at any funding level.
