That does make some sense. They are doing what is called "balanced billing" -- billing you for the amount that is different form the "usual and customary rate" (UCR) and their fee. My dentist is not in my network but they generally do not balance bill me anymore (I have also been a patient there for quite some time and the rates that my plan pays are in a reasonable range) -- it's totally the choice of the provider and is pretty common practice to balance bill. It often really depends on how low the UCR is -- sometimes they are unreasonably low.
I've only had a panoramic x-ray before getting braces as an adolescent and then before getting my wisdom teeth out 6ish years ago. The office I go to doesn't have one so they do bite wing x-rays once a year.
As for how I relax, I think I have a couple of things that help:
1. I have spent a lot time practicing deep (diaphragmatic) breathing to manage anxiety. Google it

It's important to practice when you are NOT anxious in order to be able to do it at times of high stress/anxiety. I usually do this on my way to The Chair and before dental injections and any other times I start to feal anxious.
2. I try to make small talk about anything NOT having to do with dental stuff. I often will plan this out ahead of time because the anxiety sometimes makes it difficult to think clearly. For example, I know when I go in on Monday, I will talk with the office manager and tell her that I just found out that I made it onto a charity team for the Boston Marathon (OMG -- I am soooo excited about this! I just found out yesterday, so this has definitely been a good distraction). She volunteers there every year so I know that she will be excited to talk about this. It's a huge deal for runners in the Boston area. I try as hard as I can to just act 'normal' as possible and try to pretend when I'm there that going to the dentist is no big deal (yeah, right!) -- kind of a fake it 'til you make it approach.
3. I have been seeing the same dentist for more than 6 years and I completely trust him to do his best to provide pain-free dental care and also to do really good, skilled work. I think that, because of this, as soon as I hear or see him I remember that I'm 'safe' and things will be ok.
Does any of this seem helpful?