Its very much seen as a private subject here in the UK isn't it? You don't say to people "how much do you/your DH earn?" do you, but sometimes I do feel curious. Even my best friend - I don't know! I know all sorts of deep dark secrets about all sorts of people, but I couldn't tell you their salaries. Weird. If anyone asked me what money we make as a family, I wouldn't hesitate to say - I feel neutral about it - but no-one's ever asked me!
We have friends whose joint income ranges from £30,000 ish right up to £300,000 ish, at a guess, and respect them all equally. Funny not to know, though.