With basic income you make $4000 + $1000, which removes the discontinuities associated with means testing.

Whether increased taxes used to pay for the UBI end up eating up your UBI depends on the plan and how much you make/spend. Some UBI proposals are paid for with a wealth tax, others with a consumption tax, others by cutting most of the existing programs). They usually end up being redistributive in the grand scheme.

> With basic income you make $4000 + $1000, which removes the discontinuities associated with means testing.

No, you don't. It is completely unrealistic to assume that UBI won't effect salaries in any way. Of course this is hard to test in a small scale study, but "you introduce UBI and everything else stays exactly the same" make no sense.

It's equally unrealistic to assume that UBI will exactly affect salaries by canceling them out. You're right that there will be effects, and they're likely to be dependent on job as well.

For instance basic income may mean salaries go up for the jobs nobody wants to do as people are given an alternative, while salaries go down for jobs that are intrinsically motivating.

I can't say for certainty though. My best guess is that it's going to be better than the hodgepodge of social welfare (and its complex effects) we have today.