here are a few arbitrary thoughts:
* superficially, being wealthy offers an advantage to the individual, at least in the short term. it isn't necessarily helpful to other people (e.g. how did that person become wealthy? did they do something useful that contributed to society? did they merely figure out a clever way to reallocate wealth from other people? is it at the cost of long-term environmental damage?)
* the world is not fair (not a justification for anything, just an obvious comment)
* supposing the government is socially progressive and provides everyone with basic welfare, where does the government get the money to do that from? e.g. in our capitalist society [the government's] income might come from income tax, company tax, sale of natural resources, etc. suppose no-one participated in any economic activity because the government's social programs met their basic needs. then it might be difficult for the government to maintain this [since who would be actually doing the work of growing crops, teaching children, fixing potholes, etc?]!
* some governments try to support low-income households to some degree. but there are huge advantages to growing up in a wealthy family. there is certainly no level playing field. there was something in the economist about this a few months ago.
* in itself, i do not think the goal of making money is morally defensible. sure, it can be a means to an end - but the end does not justify the means. there are many ways to make money, some of them have merit, many (most?) of them do not have any merit.
* philosophically, "philosophical" arguments are perhaps irrelevant, as we live in a very flawed society, as flawed individuals. only certain imaginable worlds are feasibly reachable from the one we find ourselves in.
* money can give you power, and status. these are useful, and you are likely to live a more comfortable life with them than without them.
For some reason now I'm reminded of something Chomsky wrote about "expanding the floor of the cage" [1]. This is more relevant if you are in a position where you do not have much opportunity or power, or if you care about those people in such a position:
> Millions of workers have become organized into rural unions which are very rarely discussed. One of the slogans that they use which is relevant here, is that we should "expand the floor of the cage." We know we’re in a cage. We know we’re trapped. We’re going to expand the floor, meaning we will extend to the limits what the cage will allow. And we intend to destroy the cage. But not by attacking the cage when we’re vulnerable, so they’ll murder us.
[1] http://www.chomsky.info/interviews/199704--.htm
edit: it is perhaps useless to think about money without thinking much more broadly about the system that money forms a part of. which human activities are encouraged and discouraged by the system? which individuals benefit? which individuals suffer? is the human economy separate from the physical/natural environment?