For new and expensive schemes it is often a challenge to figure out who will be paying for it. The proponents typically don't want to say for the obvious reason - the people paying for a universal service will probably be worse off than if they weren't so it isn't helpful to identify them (they'll just add to the resistance). But that means it is awkward to attack an idea on cost because detractors don't propose the scheme and are often dealing with people unwilling to suggest realistic costs or tax schemes. People with technically excellent arguments have to be a bit oblique in pointing out that someone has to pay and it'd speed the debate along for someone to figure out who. For a UBI, we might suspect it isn't going to be billionaires.

The fair way would be if sentences had to pattern match "I think [scheme] is a good idea and we will pay for it by [specific tax proposal].". Seems unlikely in practice though.