I wouldn't be too quick to write off the German State Healthcare system. It's (IMO) pretty good.
I suspect the doctor who treated your wife's grandmother may have only given her a few tablets because that's all (s)he had. - One of the doctors I see has given me a few tablets of a new medication, but also wrote me a prescription which I took to a pharmacy. AFAIK, the doctors expect you to get your meds from a pharmacy, rather than at the surgery.
I got the figures for income (the threshold for private insurance) from the Medhunters article I cited; I can't confirm the current threshold level.
I think your plan of getting your father in law to check with a doctor is probably a good idea; if you can retain your present coverage for a few months after you get there, that will at least give you time to check what's available and find out which plan suits you best. Good luck with that.
It's difficult to answer your question, because there are a lot of points which are not covered in your post to be considered.
What do you do for healthcare at present? Can you retain your present healthcare coverage? Will you and/or your wife be employed in Germany?
This article has some of the details on who must have state insurance and who can opt out. - It also (See the ranking) makes some interesting comments about the quality of healthcare in Germany:
Healthcare in Germany - Medhunters Medical Community According to WHO, the German healthcare system ranks at 25 out of 191 countries. The US and Canada rank at 37 and 30 respectively.
I have private healthcare insurance (not from a German Company) and I also get healthcare through German State facilities (It's more than a little complicated and it took me a while to work it out )
If I go to my 'primary provider', I don't pay anything and the bill isn't sent to my insurance company. (I'm sure somebody gets the bill, but it's not me ... though sometimes I see the amounts which are charged.) My primary provider handles routine matters, but often refers me to another provider. If that happens, I am treated as if I was a German resident patient, but the bills are sent to the primary provider.
If I choose to go direct to a specialist, or if I receive emergency treatment, I'm classed as a private patient and I get a bill which I must send to my (foreign) insurance company. They pay whatever they're going to pay (eventually ... they are rather slow) and I have to pay the balance direct to the provider.
I prefer the first system - it's far less complicated - but occasionally I'm forced to use the second. I did so this summer. After a couple of visits, I asked the doctor's secretary whether she (or her boss) would prefer to handle my treatment by referral through my primary provider and was told: "Oh, no! - The Professor only sees private patients. If you come here as a referral, you will be seen by one of the more junior doctors."
I doubt that I would receive inferior treatment, but I suspect that the Boss charges a bit more.
My insurance company - Like most insurance companies - doesn't cover every treatment and it was my bad luck that one of the treatments provided wasn't covered by my insurer, so I had to pay for that out of my own pocket. Had I been referred to that doctor through my primary provider, then the treatment would have been covered ... You can't win them all.
You said: "I have a pre-existing condition that requires expensive medications. I've been told gov't program doctors in Germany have a budget for how much medication they can prescribe each year. Therefore, they have an incentive not to write me a prescription for the full amount of meds I need."
If, for instance, you need 40mg of a particular expensive drug then I doubt you would be given 20mg to save money. If you need 40 Mg, you would get 40mg, BUT:
Healthcare is a 'scarce' resource. It's not unlimited. It may be that certain medications are not covered by the German healthcare system (just as certain medications and treatments are not covered by other healthcare systems and by insurance companies [like mine].) That doesn't (necessarily) mean you won't receive treatment, but it does mean that you might receive an alternative treatment.
Having said that, my wife was prescribed a drug while we were living in the US. When we came here, she went to the primary provider who referred her to a specialist, who re-authorised the prescription for the medication she had used in the US. She took the prescription to the primary provider, who filled it.
When the medication arrived, the price was on the packing slip. I was just a bit impressed! - That is an extremely expensive drug. The doctor agreed that she needed it, the medication does what it's supposed to do, so she got it.
I've no complaint about the healthcare I received in the US (though my insurance premiums were significant) and I've no complaints about the German system, either.
About 5 years ago a doctor I was seeing (I was living in Germany at the time) sent me to a hospital for an out-patient 'procedure'. I had to wait about a week for the appointment (not bad; it wasn't an emergency) and on the day, I got on my bike, rode to the hospital, did what I was told to do, got a bill for €525 (which went to my insurance company), got on the bike and rode home.
A year later we were in the US and it was my wife's turn to have the same procedure. She had to stay in hospital for 3 days (bored out of her skull) and the bill was $14,500. It would've been far cheaper to put her in a taxi, drive 60 miles to the airport, fly to Frankfurt, stay in an hotel overnight to recover [partially] from the journey, put her in another taxi, drive 60 miles to the hospital I went to, do the procedure, put her in another taxi and take her back to Frankfurt, give her another night in an hotel, fly back to the US and take a taxi home. It would've taken about the same amount of time, too.
The bill (in the US) was $14,500. That was the bill you would have to pay if you didn't have insurance. - The insurance company paid about $3500 and the hospital took that in full settlement.
Perhaps the 'dual billing rates' - a very high charge if you're not insured and a much lower charge if an insurance company is paying - are a part of the problem with healthcare in the US. In Germany, I gather that every medical procedure carried out under the state system has a laid-down price and that is the price which is charged.
I spoke to that 'somebody' today. He imported a US spec vehicle he'd previously used when he was assigned to NATO in Belgium and registered it locally. - As the previous guy told me, he had to go through a 'one off' inspection and evaluation process and had to pay taxes. The total cost to him (at that time, about 4 or 5 years ago) was in excess of €2500.
He also told me that as the car had Belgian plates, he was permitted to retain the Belgian registration for 6 months (which gave him plenty of time to get the checks done) but said that had he still been on US (or other Non-EU) plates, he wouldn't have been able to use the car until he had obtained a German registration.
He too seemed to think that your best bet might be to approach BMW and see if you can get them to issue a certificate of conformality. If you can, it will save you a lot of both money and time.
The fact that the car was manufactured in the EU might make it a bit cheaper ... and you certainly shouldn't have any problems getting spares for a BMW
BMW may be able to provide you with a 'Certificate of Conformality' - assuming you need one - (which would save you the expense of having the car tested independently) and you might also be exempt from the non-EU Vehicle import duty and possibly 'nationalisation' procedures - which would just leave you with a bill for whatever VAT was assessed.
I'll be seeing somebody over the next few days who has (I think) re-registered a car he brought into Germany (while he was here under the NATO SOFA) and I'll ask him how much it cost him. - I should be able to let you know by the weekend.