Who paid for you to go is not an uncommon question. Sometimes it's pre-empted or preceded by "what do you do for a living?" If you say doctor or lawyer or CEO it may end that line of questioning. I did have one guy say "Oh, lawyer, I guess a lawyer could afford to travel like this. Go ahead."

If you are traveling somewhere exotic and have a low paid job and can't explain how you have the means to travel, they start thinking about drug smuggling.