Human space flight - what a waste of resources. Send robots for the next 100 years.
But launching a human is still more expensive than launching several robots.
Right now, launching humans is getting cheaper every year. Space missions are projected to become more profitable over time as people start space mining and later space fabrication.
So I agree with you that launching robots right now has a higher ROI than launching robots.
I think we also agree there's a crossover point.
Where I think we disagree on is when that crossover point might. You say 100 years; I think with current trends it could be under 50 years, maybe under 25 years.
Why do you think it'll take 100 years to hit crossover?
In about 200 years or so, I wouldn't be at all surprised if there were more people off earth than on it.
I really wish for you to be right, but with population growth slowing down, and possibility of building floating cities or terraforming Sahara, building large orbital stations or going to mars in large numbers may be economically not viable, unless we invent something radically new.
Even the most automated of robotic factories on earth still have a number of humans in an oversight role, where they make themselves quite useful.
The same would be true of any space industry. People would be hired on for a tour in space, and they'd be paid sufficient salary to make it worth their while.