But I’m not obliged to do a full stop at Frankfurt.
Of course not, unless they send up an interceptor that forces you down. I don’t know their current fees but theoretically, they can charge you a full landing fee for the low approach (other airports like Karlsruhe Baden-Baden (EDSB) do exactly that!) making it actually cheaper to land than to go around and divert.
Sorry, but I never heard of an airport taking landing fee for a low approach. From where did you get that?
Sure, even EDFZ (Mainz International) does it.
Various UK ones do it, otherwise they would have the various flying schools within quite a large radius going there for practice approaches.
There have been cases in the UK, not well publicised, where they had no charging structure for this so they didn’t invoice it.
Some of them were airports that do not ordinarily offer GA parking space, or are “well into 3 figures” pricey e.g. Southampton and Farnborough, respectively.
My base, Shoreham EGKA, doesn’t charge for an IAP if you land from it, otherwise they do. They also charge for a touch and go, but I don’t remember the low approach and go around charging (if any). Obviously any go around charge is waived if it is due to say a runway incursion.
It is a real problem because as I say schools will fly to another airport to fly a published procedure, and they tend to do it mostly on nice (VMC) days when the place is busy anyway. It is controversial because people think they will get charged for going around from a normal but badly stabilised (etc) landing. I think in most cases that doesn’t actually happen because ATC use their discretion on e.g. windy days to not make a note of it.
N. France has long offered free approaches and I think most still do, but the UK CAA doesn’t allow flying to France for IR training, which has to be FTO based (possibly some recent developments on that one, I believe).
It depends. On a VFR go-around, most don’t charge.
But on an IFR low approach, most do. And they have to. Otherwise, ATOs would fly all their approaches there, use their rescources all the time and not pay a cent.
However, I think that the major german airports don’t do this for a one-off cloudbreak maneuver. You’ll probably have to pay DFS (15 Euros), but not more.
What about the various navigation charges, which one gets to pay some months later, when they have traced your N-reg via the US trustee address? 
Most countries in central Europe don’t have navigation charges. It is more common in places like Albania, Romania and Russia. 
DFS (German ATC) charges in-/outbound fees from bigger airports, e.g. Bremen, no matter whether VFR or IFR. That’s an ATC service fee. No problem with that. But a VFR airfield such as Mainz charges me a landing fee for a low approach? For what? For using their air? They don’t provide any service, I don’t have to talk with them at all.
Still, I’m not convinced that Mainz charges fees for low approaches. Please provide some proof. Same with Karlsruhe.
Btw, I have never been charged for practice “aka simulated IFR” (low) approaches in EDDW. The charge applies only after a full stop landing.
Sorry, but I never heard of an airport taking landing fee for a low approach. From where did you get that?
There are some things that I just happen to know because EDSB is one of our main training airfields
But you can read it for yourself if you don’t believe me, page 4, Article 1.8 in this document: http://www.baden-airpark.de/fileadmin/airpark_user/pdf/Entgeltordnung.pdf
