There's more to the quest for riches than just gaining opportunities for more physical pleasure -- it's also a quest to be admired. Studying an interesting question or creating a thing of beauty is a pleasure unto itself, and it's one which can also lead to prestige and a sense of accomplishment. Leading a virtuous life is its own reward if you believe in the virtues you've chosen. In any case, there's a strong motivation to feel that you're doing something valuable in life, and to have others in your community agree with that assessment.
Virtue can be defined as placing others' needs above your own desires. Under this umbrella, the particular acts regarded as virtuous can change as the situation changes. Today conservation -- saving as much as possible for future generations instead of a short-sighted grab-and-gobble -- is rapidly rising in value to become perhaps the highest virtue as our environment-and-fuel situation becomes more and more terrifyingly urgent. Celibacy no longer ranks as a virtue in the eyes of the general population: with effective and readily available contraception, sexuality isn't equivalent to leaving more mouths to feed, so the self-denial of abstinence is no more admirable than self-flagellation. As the human race becomes more globally interconnected, rainbows of diversity take the virtue spotlight away from piety and faith (which can be used to bolster ethnocentrism and violence). It's no wonder the religious right is so desperately angry: nobody wants their own investments to lose value. In the middle, monks, nuns, and other ascetics retain a place of esteem as they can teach the faithful to admire leaving a small footprint.
Personal achievement is a beautiful way of earning esteem. Whether you're an artist or athlete, researcher, theorizer, philosopher, or whatever, flexing your talents typically costs little (in terms of Earth's resources) compared to the joy, satisfaction, and potential good that is produced.
Seeking status (and status symbols) seems like the opposite of virtue, yet as with virtue and personal achievement, vying for status is a typical human way of convincing yourself and others of your value. To me this is the biggest weakness of the communist idea "from each according to his ability, to each according to his needs." Leftist intellectuals notice that it's bad that the idle rich enjoy a lavish lifestyle while poor children go without food or medical care. Yet if everything were equalized economically, the rich man loses his prestige while the intellectual is still admired either for his personal accomplishments or for his position as a leader. So it's hard to see pure communism as a selfless (hence virtuous) position for an intellectual to take.
A more realistic goal than equalizing wealth would be to try to narrow the extremes and persuade the top dogs to desire and value items which are less wasteful.
"Finer, not more or bigger" should be held up as the measure of true luxury. A bottle of wine that costs three hundred euros on the table of a five-star restaurant doesn't take significantly more of the Earth's resources to produce than a three-euro bottle of table wine served in a modest home, yet is an impressive display of wealth. An apartment with a fantastic location in Manhattan -- filled with original artwork -- will probably set you back more than a giant McMansion filled to the brim with rarely-used manufactured goods and accessed via S.U.V., but guess which one sets the world back more. Similarly, expensive designer clothing might be made by skilled artisans earning a living wage (rather than in a sweatshop), and the luxury food industry today can support innovations and traditions (organic farms and traditional artisans) which are more Earth-friendly than industrial farming. I'm not saying wealth is a virtue, but changing values can limit its harm. And people who want to be trendsetters can do some good by encouraging others to aspire to forward-thinking eco-friendliness.
I was over in the expensive part of town the other day, and noticed a few shops displaying handbags in the 900 to 1500 euro price range (and, no, I did not mistakenly add some extra zeros there). To my fashion-uneducated eye, the expensive purses were all grotesquely ugly. My immediate reaction was that you would have to be completely out of your gourd to even want one of those. But of course the ladies who want those purses aren't trying to impress me. (I'm happy to oblige by not being impressed.) On the other hand, if you've got money to burn and want people to know it, there are worse choices you could make. At least "taste" items are small, represent spending money on ideas (designs), and show some value for something somewhere on the education spectrum.
The guy who says "I already have four houses and ten cars, so I guess the next item on my rich-guy agenda is a yacht..." deserves more pity than envy because he's displaying his lack of imagination even more than he's displaying his wealth. America fervently believes in the Horatio Alger story, that unlimited opportunity exists for everyone in the U.S., and that it's one great, big meritocracy where your wealth is a measure of your merits. As a consequence -- since showing off good taste smells of "old money" -- obscenely wasteful over-consumption has long been the ultimate status symbol. But the connection between Horatio Alger's reward and the resulting values of "money = good, culture = bad" gets lost somewhere along the way, and we get leaders like George W. Bush: a wealthy heir who failed at the business opportunities that were handed him, and who is too elitist to show any kind of consideration for the growing ranks of the working poor, yet can still pretend to be salt-of-the-Earth by wearing his lack of culture on his sleeve. Fortunately his hypocritical example may nudge people's opinions in a positive direction. If you're going to be rich, at least make some sort of effort to demonstrate it's not wasted on you -- try to be a philanthropist or patron of the arts or something, sheesh!
So while capitalist theory holds that some economic disparity is necessary to inspire ambition and innovation, I'll quietly add that some economic disparity is not necessarily harmful. The key word, however, is some. People will work day and night to be just a little bit better off then their fellows, but it's all relative and values-based. If the Joneses don't have a swimming pool, there's a good chance you won't care that you don't have one either. If the Joneses just put up these fab new solar panels that power their house and their electric car, you might just need some too. But even if there's benefit to having a little room for economic advancement, that doesn't mean there's any benefit to extremes of wealth and poverty. It's not like the entrepreneur will give up and not bother to try to become rich if he hears that his capital gains or his children's inheritance might be a little less on an absolute scale -- being richer than others is just as rewarding even if it doesn't mean owning every resource on the entire planet. On the other end of the spectrum, no one benefits from seeing children lack basics like nutrition, education, and healthcare, particularly if the country can afford to do something about it. It's merely a question of choosing to invest in the future rather than choosing the instant gratification of gorging on pork today. In other words, choosing virtue.
The human desire to earn esteem and admiration can be what ultimately saves our species -- as long as we value forward-thinking and an eye for the future.