Professors are usually appointed as civil servants (before and after tenure). These positions are remunerated according to the salary scale for academia (“Wissenschaft”), the so-called “W-remuneration”. It differs depending on the federal state in which the employing university is located and the designation of the professorship within the scheme: Junior or assistant professors are paid in the category W1, associate professors and the like in W2 (usually not available in Baden-Württemberg) and professors in W3. These categories designate the base salary, which are frequently augmented by a bonus based on past performance (Leistungszulage).
Whether a professorship is designated as W1 or W3 is determined by the university leadership, contingent upon approval by the ministry, and is non-negotiable. The budget allocated to the professorship, equipment and the performance bonus payments are determined in the course of offer–counter-offer negotiations between the prospective appointee, the rector, the dean and the department.
A tenure track system has only fairly recently been introduced in Germany and does not work in exactly the same way as in other countries. See the following overview of the different types of professorships available at the University of Tübingen.