[nine_k]

Conspicuous consumption can be rational, or at least beneficial in the evolutionary sense.

If you are a lawyer with a good practice, you are expected to drive a nice large car. If you drove a battered old economy-class car, your clients might see it as a sign that something is wrong with you (there are several plausible ideas) and shun dealing with you. There go fat fees and investment savings.

[rdw]

Yes, I've heard this said many times about sales people. If they're not visibly wasting money, people are reluctant to hire them because they either aren't good (and thus have no money to waste), or won't be hungry (because they've saved the money they earned by not wasting it). So conspicuous consumption becomes a way to signal that the sales person is capable of reliably generating large incomes.