plasma accuracy

I've been looking at some plasma machines, and some of the accuracy
numbers they throw about seem ridiculous. I mean, the cutter itself
isn't going to be too accurate, is it?

So, realistically, what sort of accuracy level would you want to
build a table to? Do you need precision rails, or would cold rolled
with care do?

Just seems to me to be a case of why build it more accurate than it
can possibly cut anyway (therefore much more expensive), so I thought
I would ask.

Thanks

Rod