Thre is no fundamental reason why private enterprise cannot play a leading role in the conquest of space, but there are plenty of good, solid business reasons it won't. As long as getting to space is very expensive, and there is nothing of value there worth going after, it ain't going to happen. Any other conclusion is entrepreneurial fantasy.

A short term profit motive is even more important than initial funding, enterprise can always borrow capital; but it can't get financing on the promise of return on investment a century or two down the line. The history of current successful space ventures (such as communications satellites) as well as the 16th century promises of spices, slaves, furs, tobacco and gold, both bear this out.

Currently, there is no known commodity that if mined, refined, packaged and piled neatly on the moon would make financial sense under anything remotely foreseeable in the way of technology. However, there are some things that might be worth taking great financial risks for.

If energy could be collected in space, and then somehow beamed to earthside consumers, this would make it worth our while. Another possibility would be the discovery of living organisms somewhere in the solar system. This could kick-start a chemical industry based on an alternative biochemistry and the potential for profit is enormous. A third, more speculative, possibility is the discovery of either alien artifacts in the solar system, or a massive communications facility in space capable of downloading potentially valuable information from extraterrestrial civilizations (assuming this could not be accomplishished from facilities on earth). It stands to reason that none of these projects would be a money-maker capable of shaking open investor's purses unless the entrepreneurs involved could claim sole rights and control of the discovery. This is not likely to happen.

On really big projects like this, private enterprise will always be dependent on the legal and military protection of government power, so it will always be vulnerable to government greed and interference. Private enterprise may develop rapidly by providing services and infrastructure for the primary extractive industry, but the former will not materialize unless the latter does first. And the free market will never raise its own capital for these ventures as long as there exists the remotest possibility that the government will subsidize them.

My guess is the commercialization of space, if it happens, will be based on the model of such enterprises as the East India or Hudson's Bay companies: powerful government-supported monopolies backed by mercantilistic states who provide the military muscle to keep away rival states and companies. On earth, this situation resulted in 500 years of war between colonial powers and almost infinte human misery. And we should not forget, the technology that made this possible, maritime and military, already existed, along with the native and slave labor needed to actually do the work.