I don’t get this question frequently but an awkward silence is followed with a stumbled response to the likely just curious but somewhat invasive question. I don’t ask what their retirement account holds or how much their salary is, but yet I stumble.
Can’t wait for the next time when I will seamlessly say, “Quite a few but always happy for one more sale. Want one? I have one in my car and accept Venmo.”
As a reader, why do you think someone asks the question? Is it their measurement of success. Curiosity about indie authors? As an author, how do you field this question?

I haven’t been asked this one yet…if I ever do get asked I hope it comes from a place of genuine curiosity rather than a desire to belittle/bully me.
'More than I expected," offered with a smile, followed by redirection, and without the snark and swears such a question deserves. It's a nosy, stoopid question, imho, and reduces my chosen vocation to numbers, which I refuse to do. But in future I think I'll add, "And you can order it from any bookseller".