Starting in the first week of August AvangoBus.de will serve Karlsruhe-Baden Baden airport (Baden Airpark) - Karlsruhe city center - Heidelberg city center - Mannheim ICE-train station - Mainz city center - Wiesbaden city center and return three times a day.
According to their press release a one-way from Baden-Baden airport to Wiesbaden was €17.20