The short answer
Each test involves two separate amounts: the testing organisation's fee (TÜV or DEKRA) and the driving school's entry fee. Independently of those, the licensing authority charges a one-off fee for the application. On a retake the two test amounts fall due again; the authority fee does not.
There are more items on the bill than most people expect, and they come from three different places. Knowing which is responsible for what also explains why a driving school cannot lower some of them.
The testing organisation
TÜV or DEKRA conduct the tests and charge their own fee for each — one for the theory, one for the practical. Those amounts are the same at every driving school, because no school sets them. They still appear on your bill, because the school advances them for you.
The driving school
The entry fee covers what happens around the test: registration, arranging the appointment, providing the car, the drive to the test centre and your instructor's presence during the test drive. It falls due separately for the theory and the practical.
The licensing authority
A one-off charge for processing your application, regardless of how many tests you end up needing. For BF17 it is higher than for class B, because the supervisors are registered as well.
On a retake
The test fee and the entry fee fall due again. The basic fee, the authority fee, the eye test and the first-aid course do not — those still stand. What happens after a failed test is set out separately.
What is not part of it
The eye test and the first-aid course you pay directly to those providers, not to us. You need both before the application is made, and both are prerequisites rather than test costs.
Every amount that arises here is listed individually on the prices page. What makes up the total is a post of its own.