An estimate of price before construction has even begun is nothing but a guess. I doubt I need to remind anyone that large urban construction projects often go far over budget and take far longer than planned. A relevant quote: “No public transit system I’m aware of covers its costs on fares. (Musk) is the rare entrepreneur willing to bet it can. He’s willing to build this completely at his own cost. If he fails, he fails.” Source: Chicago Business.com: "What a prospective customer saw in Musk's tunnel vision" Yeah, I can see why they would give Musk the green light on this project if he promised to pay for everything himself. If Musk is personally assuming all the financial risk, then the municipality of Chicago has little to lose. I don't get it either. Musk said that his goal was to reduce tunnel construction costs by 10x, but just as you say, all he has done is buy some used boring machines. I don't see that this is a path to reducing costs. But hey, it's Elon's money. I hope he and his engineers do figure out how to substantially reduce tunnel construction costs, but real-world experience shows that Musk tends to be too optimistic about such things. For example, he said he could reduce orbital launch costs by 10x. SpaceX has reportedly been able to reduce them by about 5x. That in itself is remarkable; an 80% cost reduction is astounding! But still short of his goal. Per mile of track, I have no doubt you're correct. But measure it on passenger-miles, and that's a very different equation. It's the passenger-mile figure that indicates running costs, which seldom if ever are completely covered by ticket costs, so the municipality has to kick in a subsidy. But a subsidy of mass transit may be very beneficial for the economy of the municipality. By making it easy and cheap for people to get around, that boosts the job market and encourages trade. Contrary to the hard-right crowd which believes everything should be able to pay for itself, subsidizing mass transit is a win-win for the entire community, so long as the subsidy is justified by an economic boon. It's when they build "bridge to nowhere" type boondoggles at taxpayer expense, that we taxpayers should object very loudly and very firmly. But to return to the subject of this Chicago mass transit project: The thing is that subways are pretty much a known quantity. We know pretty well how much it costs to build one and how much it costs to maintain one. Rational decisions can be made on subway construction. Contrariwise, Elon is offering a rather different plan whose true costs, both for construction and for maintenance, are unknown. Furthermore, he's offering something so different that it will be utterly incompatible with current subway systems. Right there is a serious problem, and a serious barrier to expansion if the pilot line does prove successful. Any mass transit system, ideally, should carry passengers from origin to destination with a minimum number of transfers. Every transfer means another wait, and the necessity to build another station... which adds cost. A subway system with a bunch of Boring Co.-type branches won't be an efficient mass transit system. This should be an all or nothing thing: It should be either all subway, or all Boring Co. type transit system.