...The numbers get interesting when the gravity is low: Assume, say, 500 cubic meters per person. Then take the area of Manhattan (60 square km), and give it an extra dimension to work with, giving you 465 cubic kilometers. That's a population of 1 billion....
This is my first post on this site because I could not resist responding. Love the enthusiasm but the predictions are crazy optimistic. Let's say as an aspirational goal, we hope that eventually, 1/1000 of those people would spend 1000x that amount for a trip to orbit for two weeks ($1.8 million ticket price, 22k people per year)It's not a direct relationship. Data show (http://space.alglobus.net/papers/Easy.pdf, see page 27) that far fewer people will pay big bucks for space tourism than you're assuming.
I think the lesson here is that the world needs updated data on what people/organizations would pay for "spaceflight participation" aka tourism. Both your data (1999) and my data (2001) are woefully out of date. Those surveys were taken pre-9/11 pre-Great Recession pre-lots of stuff. Until the data are revised I think we are spitting into the wind.
That said, my gut tells me that ULA's Cislunar 1000 plan (or whatever it's called) is the best prediction i.e. 1000 people living in orbit by 2045. Why do I think this? Because 1. it's ULA and if anyone knows anything about how fast or slow space development will go, it's those guys.
2. they're a fairly conservative company
the explosion of venture capital funding now being put into new space companiesIt's funny you write that because I literally just finished an email exchange with a VC guy in the Pacific Northwest who loathes investing in space because he has lost so much money in it. Yes there is a lot of money going into space ventures but how much of it is profitable? Not too much. Not yet, hopefully. And certain not a lot at all focused on human spaceflight.
If the 1999 survey says just under 50% of people would travel into space for $50k, adjusting for inflation, it's not unreasonable that the same would be true now for $71k. Western culture hasn't changed that much in 15-20 years.