My bike isn't an expensive one. However, I have been asked and I tend to be vague even with people I know well. For those I don't know, I'd probably downplay the question while changing the subject.
OR, respond with something similar to what was posted just above..
"Thanks, but it's really not all that.. it's probably worth about $50 today. If I had it all to do over I'd likely get a Huffy."
