Wow, that seems to be pretty high indeed. I am not familar with the US healthcare system, so it could very well be a lack of competition in the health insurance market, but it could also be due to what we economists call adverse selection. (WARNING: boring economist's blabla
When quality is hard to recognize on a market (in this case, quality is the health risk of people who demand health insurance), only bad quality might be traded (here: the insurance company thinks that you are high risk when you apply for an insurance policy, so they offer only high fee / high anticipated risk contracts).
In Germany, there exists forced health insurance for people who work (including their family members) financed via a quais-tax on labour. This amends the adverse selection problem and to make a number example: average monthly wage here is about 3500$, the quasi-tax rate is about 15% so 500$/month go into the health insurance system, clearly much less than the 900$ you mentioned.
I know little about health care systems, but a) insurance for everybody is important to avoid the adverse selection problem and above all, do we really want to deny poor children access to decent health care ... and b) mixed systems, involving some form of government activity, seem to work better than dogmatic pure market / pure government ones.