I agree this is all a huge pain. I've been burned on "this test cost you x because of the facility it was done in and if you had gone to one of our partner labs (which you'd have no way of knowing without calling us), you could have had it done in for 1/4x".
I recently learned that there are 2 different codes involved and that it's the combination that matters.
1. The diagnostic code - the reason why you need that test
2. The procedure code - what the test is
My insurance tells me that their coverage (as in whether they cover a service or do not) is different for the same procedure code with a different diagnostic code. I'm not sure if that implies that their coverage price for the same procedure code also varies by the diagnostic code.
Your doctor can give you both codes for the test they're prescribing. In theory, your insurance company can tell you what they'll pay for the combination, and then you can contact each lab / hospital / service provider to get an estimate for what they'd bill. It's unclear how much recourse you have if the bill turns out to be significantly different than the estimate… that is once the bill actually arrives, sometimes 30–60 days later. I'm not sure if the service provider's bill varies for the same procedure code with a different diagnostic code.
Admittedly this is all a huge pain and with my insurance company at least, cannot be done online, you must call and wait. It's all such a time sink that I usually just get the service done upfront and hope. Sometimes the end consumer cost is practically free, sometimes it's hundreds of dollars or more.
It should be more feasible for us to know a rough estimate for a procedure across providers upfront.