I don't think this just affects "rich" people.

It could also be that Waterluvian had a low income and that affected his relationships.

Or it could be that it just differed in a direction (up or down) that his peers didn't expect or appreciate for whatever reason.

I can think of a lot of reasons revealing my income would affect various relationships I have (whether that's a good thing or a bad thing isn't relevant), even though I wish it wouldn't. Information about money does change the way people treat you.

When I was a kid, people knew my family wasn't doing so well and I'd get lots of well-intentioned charitable offers from friends and friends' parents that just made me feel really bad about myself, so there's one way that having a lower income revealed can affect relationships in an apparently positive way that's still uncomfortable.

I had coworkers that where hostile to the very idea of equality. Get paid the same as them? They were worth twice as much. Take a pay cut in exchange for some other bonus? They deserved the bonus more than you and they would get it without the pay cut (they didn't, especially not after trying to add their own terms to it). There was nothing positive to informing them of the pay of anyone else.