The high energy cost of getting into space can not be ignored- it is a significant part of the problem. One solution to this problem is the sub-orbital route. Branson is correct in seeing that this has significant potential. And as far as I can tell it seems like a lot people get this, and govt seems to be doing as much as can expected to encourage this. But sub-orbital path isn't easy and we will see if the players involved can make this viable. In simple terms sub-orbital cuts the high energy cost problem in half and it as a somewhat ready market to serve- both passengers and even cargo.

BUT high energy cost is not biggest problem or only problem- it's possible to completely throw out the suborbital pathway and still make space development viable. The keyword in all this is markets. The first market I would focus on is the launch pad market [sub-orbit is bypassing this by using airports, but orbit and beyond *probably* requires launch pads]. Personally my favored approach in regards to launch pads is using the ocean as a launch site. Now, I have specific ideas about this, but I won't bogged down in them. Let's move on to next important market: rocket fuel in space- gas stations in the space environment. Again I have specific idea about gas stations.

But let's get to the gold bricks on the Moon thingy. In today's nonexistant lunar sample market, lunar dirt is valuable- more valuable than gold bricks. If you could buy lunar dirt $1-3000 per gram it would a reasonable price to pay. A large part of this price is due to it's rare nature- hard to buy. The reason gold or diamonds are expensive is because scarity of these things- they are useful and sentimental, but the difficulty of getting them is large factor in it's price. Diamond prices are controlled largely by molopoly and gold has long history of being equal to money- gold is money, many many people see gold as "better" than "paper" money. According to Wikipedia "all the gold ever mined totalled 145,000 tonnes". So there hundred thousand tonnes of gold in the world and it's somewhat rare or precious- if you divide total gold by total people [6 billion], each person would have about an oz of gold- so it is rare stuff and btw everyone would poor if gold was actually the only form of money- not mention the hassle trying buy say 100 billion company such as Google [dump trucks of gold being dragged around].

But anyhow, if the amount lunar dirt in this world were as high as 100 tons then lunar dirt would still be very rare, if you "mined" and transported 1000 tonnes of lunar dirt to earth per year for 100 years, lunar dirt would still be a rare as gold.
Now people generally don't accept the idea that there could be market for sizable quantity of lunar dirt. I say there is market for at least at rate of 100 ton per year for decades, but I can't promise what the price will be. But I also can't promise what price of gold will be- and gold is a very, very, mature market- it also a very competive market. But the quantity of gold mined largely depends on the cost to mine it.
My point is that lunar dirt is just one market- and like a gold from a gold mine, lunar dirt should depend upon the cost to mine it. The question should not be how high a price can you get for lunar dirt, but rather what way can lunar dirt be mined and transported to earth at lowest cost and therefore be able to sells lots of quantity at the lowest possible price [that pays your costs and gives you enough profit so you invest the capital to expand your business- more dirt, different kinds of dirt, or something different like mining iron]- the retailers will try to get the highest price.

Consumers of lunar dirt will try to evalute what is good price by looking at all factors- and they could even choose to pay more for some product simply because they like the idea of supporting "some cause". Large part of value at consumer end, would depend upon marketing].

Lunar dirt miner would want buy rocket fuel on the Moon to ship it off the Moon- the lower the price the better- $20,000 per lb is too expensive. $5,000 per lb might be a very good price- but it depends reliablity, when and how much. Rocket fuel supplier wants water and power at low cost- but again reliablity, when, how much are again factors.

Now, you might say where is the *real* value in all this. I would say the big large scale value are things like harvesting solar power [even nuclear power] in space environment and delivering this energy to earthlings- a trillion dollar market. Colonizing space- Mars, Moon, Earth orbit- another potential trilion dollar market. But before energy is cheap enough to ship to the surface of Earth- energy will used in space for manufacturing. This starts with simple and cheap make stuff like rocket fuel, and things in lower demand in near term but still fairly simple Iron/steel products for space infrastructure [mining machines, building structures, big project stuff like observatories, mag lev type launch structures, etc]. Simple components for solar collectors- structure, mirrors, etc.

Big picture: What is needed is market for energy in Space- current cost/price of energy in space is around $50 per kwh- getting it to around $10 per kwh is fairly easy. If you could essentially buy any quantity of electrical power anywhere in space for about $10 per kwh, this would drive down costs of doing anything in Space.
There is no shortage of water in Space environment- cheap water [$500 per lb] plus cheap electrical power $10 per kwh allows one to make cheap rocket fuel.
At $100 or less per lb water and $1 or less per kwh giving rocket fuel at couple hundred dollars per lb in at Earth, [and similiar prices at Mars] makes colonizing Mars a possiblity- not with Only NASA guys, but weathy private citizens or scientists. And the moon becomes more attractive for industry and tourism.
But at $1 per kwh you still aren't cheap enough to sell power to earthlings- you need around cost 10-20 cents per kwh to get any market on the Earth surface. At 5 Cent per kwh and you start to break into the trillion dollar earth energy market- and at around 1 Cent per kwh you dominant the market.
The space environment because of it's nature allows one to get to point of providing cheap power [and products] to Earth, but to get to this point will take decades. It starts by starting small, establishing markets and competive market forces which drive costs/prices down.