I feel like I’m paying way to much for my new insurance. Should I get a new plan?

Background info, I started a new job a few months ago that does not offer health insurance. My girlfriend, whom I’ve lived with for nearly a decade, works for the state (New York) and has great coverage. She looked into it and she could put me onto her plan as long as we prove we share a life. We had to upgrade to a family plan and pay with post tax money, plus take on imputed income, but from what she was told it would come out to about $400-$500 per month. Not great but still my best option

Cut to this week when my insurance is finally reflected in her pay. It ended up coming out to $522 including taxes in this one biweekly paycheck(breakdown at the bottom). I asked her to find out what is going on, she found out that $100 of that is to pay for my insurance throughout July, $100 will be taken out paycheck for the next 5 checks. Even when that done $844 a month seems like a lot for one person’s insurance.

Are we doing something wrong? Why is it so much more than we thought? Is this remotely worth it for someone who goes to the doctor less than once a year?
Breakdown from her paystub:
Imputed income regular $246.84
Imputed income Special $200.31
Regular after-tax Healthcare $207.38
Special After tax Health adj $100