I personally don't mind telling anyone what a repair to our house cost, as those who ask would be considering having work done to their home.
I agree it is no-one's business how much your pension is.
If anyone was cheeky enough to ask me, I would say that I have the standard pension from OAP for a married woman and a little extra from the two unions I belonged to, but not state the amount.
If the person then asked me how much that amounted to, I would probably say, "Sorry, I don't like discussing money." and change the subject. If that didn't work, I would make no bones about saying, "Well, that is none of your business, is it, dear?" thereby making it clear that I had taken offence.