Manchester City parted with a hefty sum when they brought Leroy Sane in from Schalke 04 in the summer of 2016, but they could still be in the German side's debt if they win the Champions League.
Pep Guardiola had a €50m transfer sanctioned back then, but there were also performance-related add-ons, as well as add-ons relating to the team's success.
According to Bild, Sane's former club stand to make even more cash if City reach the Champions League final. Schalke will rake in €500,000 if the Citizens reach the milestone, and the sum will double if they go all the way and win the trophy.
Sane's first season in England proved fruitless, with City failing to bring in any silverware. But this term, the Etihad side are in pole position to win the Premier League title.
They will be facing Swiss club Basel in the Champions League round of 16 in February and March, and are obvious favourites to go through.
They do have a good chance to stake their claim in Europe this season, but Schalke do have a few more years to cash in even if they don't, as the opportunity will remain until 2021, when Sane's contract expires.