Sending rockets to another solar system would be cheaper than the tunnels depicted in this video. I'm not even kidding.
Where is all that material going to go? There's so many tunnels there you could build a small mountain with it. Maybe he can team up with some sea-steading outfit and build a small continent off the shore of San Francisco.
You'd need three or four orders of magnitude reduction in tunnelling costs to make that anywhere near affordable, and even then you'd still have unbelievably complicated logistical issues. How much concrete do you need for those tunnels? What about ventilation? Safety procedures? Flood control? A single one of those could cost upwards of a billion dollars and I'm not sure there's a lot of cost savings by doing more of them, the complexities don't scale that way.
The more you dig, the more you're likely to hit something expensive you're going to have to pay to fix.