"There are mining colonies, prison colonies in harsh habitats, cultural experimental colonies, religious colonies, etc. But for any of them to last or prosper, they had to be economically feasible. And the most successful had all the resources necessary for survival in situ."

No city, town, village, family unit, or no nation or vast empire in the history of humankind has had all the resources for survival in situ. And I would say that Planet Earth doesn't have the resources necessary for the living creatures on it for it's survival- though planet earth the rock, does just fine.
The galaxy and beyond is our biosphere, we just don't know it, yet.

"If enough of Mars is prospected, everything needed for subsidence living may be found there. If enough is found within a reasonable radius a seed colony might well be viable. I wouldn't expect much growth like bacteria in a harsh environment, but just returning knowledge could well support a small colony to pay for occasional hi tech resupply."

I'm not very interested in space colonies that can only manage subsidence living- I'm more interested in Mars the Superpower or the Hong Kong Moon, Sol's Spaceport, and/or Mercury the heavy industrial planet, and Earth, the Home World- excessively rich, decadent, and highly civilized.

"I agree the key to accelerating the ability to profit in space is reducing the cost to orbit. My own expectation is that it will take something like a space elevator breathrough to truly bring about rapid colonization."

I don't think there is much hope in the idea of space elevator getting us to orbit cheap. And I don't think getting the cost to orbit has to get much below $100 per lb for there to be things like Mars colonization or mining asteroids. Earth orbit is halfway to anywhere, if costs are $100 per lb for 9.5 km/sec from Earth that's pretty cheap, now say it costs $500 per lb for 9.5 km/sec from low earth orbit, high orbit, the lunar surface, or Mars surface. This means one could get one way ticket to Moon or Mars for about $100,000- and return ticket could the same or half as much. If the *minimum wage* for anyone in Space is about 1/2 million dollars per year including food and board, then you shouldn't have much problem with getting into space if you want to go.