If you've visited a doctor that was outside your insurance company's network you may want to look into how much they charged.  From an Associated Press article about health insurance companies being investigated and hit with fines:

Rockefeller and other congressmen, along with doctors and consumer groups, say that more accountability and transparency are needed in how insurance companies determine out-of-network rates, and that patients need to understand how it's done to avoid sticker shock when they get their medical bills.Typically, health plans will pay a set percentage, say 70 percent, for an out-of-network visit.

But unknown to many consumers, when patients go out of network, their plan doesn't actually pay 70 percent of the doctor's visit cost. It pays 70 percent of what it determines is the "usual, customary and reasonable" cost for the procedure or doctor's visit in question.

Insurance companies determine that cost themselves or use figures from a database of their choosing, and there's scant regulation or oversight of how they do it.

Don't you love it?  This is akin to me saying to you, "Hey look, if you pay me $50 a month I'll agree to pay for 90% of any repair you need to have to your car as long as you take it to one of the following garages.  But if you're stuck on the road and need to use another garage I'll pay 70% of what I think are reasonable charges.  Now I have this wonderful database of what is reasonable to charge for any car repair so don't you worry about it."  Then when you get the oil changed at a garage outside the network and they charge you $25 but my database tells me a reasonable price is $5 then I'll pay 70% of the $5 bill and stick you with the rest.  But here's the kicker: I won't ever tell you what my "reasonable" rates are so you'll just have to live with it and when you're stuck on the road you'll just have to hope and pray that the nearest garage's rates are within shouting distance of my "reasonable" rates.