The point is that Sessions lied on his ethics questionnaire. The amount of money isn’t important. This should have been disclosed. If the income is so negligible that it doesn’t matter, there would have been no harm in disclosing it.
This comes on the heels of the revelation that when asked to provide ten civil rights cases that he was “personally involved” in, he lied about that, too.
Sessions is a liar. What’s more, he doesn’t care. It’s as if he knows lying is an OK thing to do in this new political climate.