When I'm at social gatherings/parties, people would enquire about my job and, because I'm an app developer, they think I earn substantially more than I do. (Oh, the joy!) They then follow up asking about my job with something along the lines of

"So, how much do you earn then?"

What would be a valid response when someone asks this question, as this information isn't something I feel comfortable giving out.

Note: I don't care too much about where data protection/professionalism is involved, i.e. a recruiter asking me how much I currently earn for them to gauge how much I would like to earn in another job or when applying for a loan (as a couple of examples).

Update: if you're wondering why. ^{an interpersonal skills user asked a question about it}