You think leaving earth is the solution? The only place we've evolved to survive on.
In a billion years, when the Sun is hotter and Earth's oceans have all dried, it's probably not going to be a great hang any more.
Once day the earth will almost certainly cease to exist and intelligence will have to find a new home of some kind. We have probably got a couple of billion years though if we are careful and I have no idea what intelligence will evolve to over that timeframe.
The issue isn't the cheap junk; it's the demand for the cheap junk. Things would be far more sustainable if people focused on reducing their consumption habbits, as producers would be run out of business.
Externalities: any negative externality upon an involuntarily third party can become illegal via law. This can cover things like littering, servitude, etc.
Monopolies: the free market has yet to produce a monopoly that increases prices for consumers if there isn't a natural monopoly. The gov deals with allocation of naturally constrained resources such as radio frequencies.
Imbalance of power: just save more. Save enough so you can wake up comfortable with the idea that you were fired overnight. It dissolves any power imbalance when your boss needs you as much as you need the income.
1. taxes that force corporations and individuals to pay for the negative externalities / social costs of their actions 2. regulation (e.g. stop allowing planned obsolence, mandate the right to repair etc.) 3. government spending into R&D, incentives and subsidies for renewables etc.
Anyway, my point is that the issue is basically one of co-ordination and political will. It obviously doesn't help that many Americans (and Australians too for that matter, where I live) don't accept the basic facts of the situation (before we can even discuss solutions).
Again, what does "political will" mean? What are you going to do to those that disagree? Lock them up? Exterminate them? What is the solution to force people to do your bidding, and has it ever worked?