You're talking about launching a Mars colony, to build a massive industry, to provide materials for Earth-orbit systems... that looks like a massive complication to say the least. Yes, Earth launch costs are high -- but those exact launch costs would be necessary for almost every equipment put on Mars, at least until you have a large self-sustaining colony. Imagine the cost of power that needs solar panels brought from Earth, necessary tools, the costs of maintaining the crew, ... . $50/kg of steel produced under those conditions seems absurdly cheap.

And then to sustain this massive operation you need a massive demand. You'd need millions of tons of steel of demand to make the colossal investments (of perhaps billions/year) viable. And then the demand for the primary applications needs to be even larger. I don't know much about the applications you've cited, but I'd find it hard to believe you could get demand in tens or hundreds of billions per year. They look essentially like niche applications that can be fulfilled by a low-cost launch system. Remember that the FH costs about $1700/kg (and cost probably be cut in half or better with several billions in annual demand).

I.e. I'm not convinced. That said, I think under a very long term (perhaps by the end of the century), the objective of a self-sustaining colony is worthwhile.

Before economic viability of any enterprise, a massive amount of systems will need to be developed enabling manufacturing basic tools and materials in situ. It's basically reinvention of industry from scratch but with much more strict requirements and much thinner margins for sustenance. A first step would be probably local production of solar panels, food, structural materials, habitats. The basic elements of self-sustenance. Then gradually moving up the technology ladder until import dependence from Earth would be at a minimum. Only then it starts to become viable and thinkable to have small martian exports for orbital systems, tourism, culture and media (I imagine showcasing life on Mars would get quite an audience on Earth), perhaps low-bandwidth scientific computing. This will probably take centuries but is an important step for humanity. Sooner or later we have to get off this rock, there's an entire universe out there waiting for life...