Usually the employer is paying a portion of the costs too.
So it could be that they pay another $450 themselves, and the total cost is $900 split between you and the employer.
The portion the employer pays is also considered part of your compensation, but the employee is often not aware of it.
Meaning people end up paying a lot more than it seems, because part of the reason we can’t get higher wages or some other benefits is that they are already paying more for you than you see in your paycheck.