Being a developer myself I'm often in this situation and it all depends on "who's asking" maybe it's someone who doesn't think it's a big deal because of their culture.

In any case it's custom that the person asking provides their information first (Asia for example) so just ask back "why, how much do you make?", that way they can answer honestly if not that will defuse the situation.

Of course if they are being friendly just humorously say "not enough man, why? you got an offer?".