I'm a contractor through a medium-sized employer of about 1000 people. My family of 5 (wife + 3 kids) pays about $1200/mo for our BCBS group medical+prescription PPO. Dental is another $50/mo. No vision coverage -- paid out of pocket for laser surgery about 5 years ago. My employer pays half and I pay the other half. We have no deductible, $10 co-pays, and $10 generics prescriptions. We are a generally healthy family, eat well, and exercise (triathlons!)
We had one kid, it was going well and thought "lets just have one more"... ended up with twins. Our twins were born last year, 10 weeks early due to an emergency c-section after the wife got sick from our oldest kid. It was $10k each for the c-sections (you'd think there would be a discount to get the second one out!) After all the delivery expenses plus wife's week in the hospital the total delivery cost $30k. The girls then had to stay in the Level IIIC NICU for 6 weeks. Total amount that the insurance company PAID ended up being just over $300,000. The providers asked for about $500,000. Only thing they didn't cover was the $500 ambulance ride to the hospital. We spent about 3 months getting them to pay for the c-sections due to an incorrect billing code that neither the provider nor the insurance company seemed to care about fixing.
Overall it seems pretty expensive, but I hardly ever have any problems with them. I've never tested it for anything serious besides the twins, however. When comparing prices, make sure to factor in both the employer and employee payments. I have no idea where these $300/mo plans for a family of 5 are coming from. I looked for an individual health plan 2 years ago when I was thinking about going out own my own and at first BCBS said they wouldn't give somebody an individual plan after they had been on a group plan. Finally they gave us a price of $1500/mo.
I often review the claims when the insurance company sends them to me. It is almost universal that the provider asks for 2x to 4x more than insurance ends up paying. I'm not sure if I'd get a discount or not if I offered to pay cash before a regular visit.