Can't comment on the HOV sticker, but from looking at prices a couple of months ago, $12.5K doesn't seem unreasonable for an Insight in the western US, certainly not in California. If you look on EBay or other online listings, the ones at lower prices will be in the midwest or east.
Supply and demand, I guess
So the question becomes, are the ones back east enough cheaper to cover the cost of an airplane ticket?
Supply and demand, I guess