This article has several errors:

>The Musk “Loop” would have a capacity of 2,000 passengers per hour in each direction, which is about 60 percent of the Blue Line’s current, mostly-under-capacity average hourly ridership.

The RFQ[0] makes clear that the intent is to compete against taxi and ride-share services, which comprise 52% of trips in the 2015 estimate, to CTA Rail's 20%[1]. The article says "the Blue Line works pretty darn well", but revealed preferences tell a different story.

I can't find what O'Hare Xpress LLC (the other finalist) proposed, but the RFP[2] required respondents to specify "maximum passenger capacity: (i) per 15 minutes; and (ii) per hour". The JFK AirTrain was designed for 34,000 riders per day.[3]

>Most transit moves horizontally, some moves vertically; the concept for the “Chicago Express Loop” is to do both.

The tunnel will terminate at Block 37, where Chicago already has an unused, very expensive, giant subway station. This concept doesn't include elevators, as described so far.

> The writer and transportation researcher Alon Levy compiled the grim per-mile pricing of recent tunnel projects for CityLab in January, shown below. This table gives a sense of how extraordinary Musk’s project would be on a cost basis—and how improbable.

This cherry-picks a US price chart from an article[4] that's entirely about how tunneling is inordinately expensive in the United States compared to the rest of the world and refutes the idea that labor is the main cause. The cited article even has a pull-quote that says "There’s no reason why building subways and light rail in sprawling cities should be as expensive as it is."

>If the Boring Company’s cost projection of $1 billion is anywhere near accurate, that pencils out to $55.5 million per mile—far and away, the cheapest construction cost for any subterranean transit line in the U.S.

That should be $27.8 million per mile ($17.3m per km), since you'll presumably want it to go in both directions. This is low even compared to European transit,[5] but those tunnels are 2-3x the diameter.

Really, this project is a Loop mostly in name, diameter and rolling stock — it doesn't approach the ambitious concept of operations (elevators, dynamic routing, and car access) that is planned for Maryland and LA. That should alleviate a substantial part of the technical risk, leaving it mostly as a financial risk for investors.

Since (like most infrastructure) tunneling mostly consists of fixed costs, the most likely failure mode is not reaching completion at all. Once it's complete it's likely to be cash flow positive even if it has a poor or negative return on investment, so there's little incentive to shut it down. (This was echoed by Musk in the press conference.)

[0] http://chicagoinfrastructure.org/wp-content/uploads/2017/11/...

[1] Taxi/Uber: 5,164, CTA Rail: 2,011, Total: 9,956. n.b. These ridership estimates are for daily one-way trips, with total daily trips being twice those in the table. https://i.imgur.com/naVUjnA.png

[2] http://chicagoinfrastructure.org/wp-content/uploads/2018/05/...

[3] https://www.bechtel.com/projects/jfk-airtrain-jfk-2000/

[4] https://www.citylab.com/transportation/2018/01/why-its-so-ex...

[5] https://pedestrianobservations.com/2013/06/03/comparative-su...