Employer-based plans typically have lower premiums because they are, by definition, groups of working-age and (in most cases) working people. They are younger and less sick, so insurance costs are lower. (Dependents are typically more expensive.) This is the reason that companies, once they reach a sufficient size, self-insure, because they are carving out their younger and healthier population from the broader population. Plus, there are savings gained from administrative costs as well.

Selection of plans or providers is not the problem, especially with the current popularity of PPO plans.