It should be noted that this isn't normal! He may get away with it because he's a supreme court justice, our supreme court sucks right now, and our constitution provides insufficient checks on the supreme court's power. But there's a reason Pro Publica did an exposé.
This whole expose is about the weakness of the disclosure rules levied on Supreme Court justices, the gaps, the amount open to interpretation. The only assurance you have is that some level of compliance is normal because a disclosure happened before.
"hey look, they actually disclosed something! good thing I don't live in this *other* corrupt country in the world where you would be disappeared for saying this! American exceptionalism!"
We just found out about this recently. How do we know it's not normal? This wasn't even the only thing, he also received multiple all expense paid luxery vacations from rich people. Surely his fellow justices have questions about his exotic all expense paid trips. If anything I would assume they are doing similar things until proven otherwise.
Impeachment by the house and conviction in the senate afterwards have high bars. Impeachment doesn’t happen very often, only once for a Supreme Court justice (and the senate didn’t convict).