Rand points out that you can carry a lot to orbit without a space elevator for some number of billions of dollars. You can also carry a lot of people in a ferry for the cost of a bridge. But once traffic gets high enough, you get economies of scale. There are actually several confounded questions about the cheapest way to GEO and beyond here.
First, it is very cheap to go from GEO to the planets with an elevator since you are on the downhill side of GEO and you slide out to the planets without any lasers or propellant.
Second, optimal energy to obtain orbit might be better to be hauled along. Maybe a climber could generate enough electric power to climb itself by burning LOX and kerosene in an internal combustion engine. No energy lost to air resistance. No energy lost to following an imperfect trajectory.
Third, optimal propulsion system might be a rocket engine. A rocket designed to go up an elevator would be a lot more capable than one that goes in free space.
Fourth, staging can be used with elevators cars to increase payload fraction in elevator cars. Stage 1 could just slide back down the elevator. Stage 2 could hit the brake and do a full systems checkout before moving up. The occupants could even get out and manually disengage the stages or something.
Fifth, the thing could even be refueled at 50,000 ft by some kind of a hovering balloon or vto refuelling craft. The balloon could even make it so that the last 50,000 feet of elevator at the bottom wouldn’t weigh down the thing. This is analogous to air launch or balloon launch.
Finally, there is the economics question. Will there be sufficient demand to justify a high capacity lifter of any sort? The marginal cost of ELVs is high. But the average cost may be lower for low mass to orbit (and beyond). This gets back to the bridge vs. ferry question. If it can be shown that the bridge is more profitable than the ferry, it is worth the billions that terrestrial bridges cost. Or it might be justified anyway via tremendous national prestige and driving down marginal costs even if it is a money loser (like, say, the Chunnel which cost $15 billion or so). I think demand is surely a matter of when rather than if. Demand for orbital space tourism will grow as the number of centimillionaires grows even if nothing else does.
The business case for elevators has not been scrutinized nearly as much as the one for rockets. For example, why not leave the spool for the second strand at the bottom of the elevator and send a climber up unreeling from the bottom as you go and send another “zipper” unit up after? What about suborbital jaunts for folks that don’t want to go all the way to orbit? It might even be cost competitive with airplanes for skydiving. As long as you are sending a newspaper roller up, you might as well print something in ink that will evaporate before too long. How much to print a 100,000 kilometer long love letter? Point-to-point hypersonic drop ships.
It is not necessarily true that space cannot warrant two pork infrastructure projects: a cheap RLV and an elevator. If you put it in the highway bill, you only have to compete against the dubious last $500 billion of infrastructure where trillions have already been invested. Bridge to nowhere indeed. The GEO elevator stop could even be called “the Middle of Nowhere”.
A space elevator also can be thought of as a national work of art. A modern pyramid. The longest film strip. The longest playing highest fidelity 8,000 track tape. So Bill, would you like to say to Paul, “Keep your laughing gas and rubber, mine’s made of diamond.”? How many carats in dozens of twenty ton strands? Work it right and get the ends of the nanotubes to join up and the whole thing can start as a single molecule, a single CNT lightyears long.
The promise if we can get orbit and deorbit down to a small multiple of the fuel cost whether via awesome RLV or awesome elevator is substantial. The cheapest way to get there will be a matter for competition to solve. Whether it is competition for Government projects or commercial service will hopefully be decided in favor of the market by capitalizing both projects in the st0ck market and proceeding to get them built.