My doctor is defrauding insurance company?

I went to see two different gynecologists in same county but different cities within 1 month for EXACT SAME check-up/test(1st trimester pregnancy). Instead of charging the insurance the same or similar amount, one doctor charged $680 while the other doctor charged $130. Is one doctor defrauding the insurance or is this normal variance between different doctors? I live in Los angeles county.My doctor is defrauding insurance company?
I would question it. Call both offices and ask exactly what was done and the charge for it and then compare. If they are exactly the same something is wrong and this is why insurance costs are through the roof. I wouldn't put it past any doctor. I've had an ENT charge me $560 for a 5 minute visit and all he did was feel my glands under my throat. I'm in the process of writing a letter and reporting him. I don't think they should get away with it.
If the Insurance paid the Doctor then it normal.