"A few enthusiasts still think rail-guns are a good way to launch masses into orbit, but I think we're on the wrong planet for that trick. "

I think using the standard chemical rockets is a perfectly acceptable way of opening up the space frontier.

Rail guns [or a broader term, mass drivers] will work pretty good on the Moon [and elsewhere].

{Mass driver:"A mass driver is a method of spacecraft propulsion that would use an electromagnetic accelerator to move a payload up to high speeds."
http://www.websters-online-dictionary.org/definition/mass+driver
[Personally I generally use the term mass driver in an informal sense to mean any cannon-like way of accelerating anything- whether you use chemical, electromagnetic, or rubber bands. I suppose others might use term, catapult, instead.]}

Using chemical rockets I see no reason why payload cost couldn't be lowered to around $100 per lb- or said differently I see no reason why the cost of chemical rockets couldn't get down to the price range of 2x to 4x their fuel costs.
Mass Drivers of various sorts may have fuel/energy cost of less than $1 per lb of payload delivered, but chemical rocket also have a "relatively" low fuel cost of around less $50 per lb of payload delivered to orbit.