That’s two separate factors. Different insurance plans have different contracted providers, and different employers subsidize different portions of their employee’s health insurance premiums. Some employers might subsidize 50%, some 80%, some $100, etc.

I was referring to the cost of insuring someone, regardless of who is paying. I’ve compared costs on healthcare.gov to employer based options in a few states, and they’re not far off from each other unless the employer has many younger employees and few old employees.