Captain Smithy:
"7) Folks who continually ask how much it costs to fly.
Picture scene if you will; talking to colleague at work, old friends I haven't seen for a while, chatting up bird in nightclub, whatever.
"So what hobbies do you have then?"
"Oh, I'm a pilot."
"Really? How much does that cost then?"
What does it matter to anyone else how I spend my meagre wages? Without fail the first question uttered when the "P" word is mentioned."
My suggestion is to answer that question by saying that you have absolutely no idea how much your hobby costs.... thus neatly openning a completely different can of worms.