I bet this is due in large part to the availability of credit over the last few decades. Credit has allowed lower-income people to "play the part" of the wealthy, giving rise to the distortion. In particular, interest-only, 0% down mortgages, low or no-interest credit cards, and car leases let someone making $50,000 a year drive a Mercedes, live in a million-dollar house, and buy fancy toys like flat-screen TVs and Jet Skis. I think the vast majority of the public would base their perception of wealth on material possessions such as cars, houses, and boats rather than the amount of money in savings or investments. This could explain the discrepancy.