### One-sentence description Event price can change after registration start ### Current behaviour / Reproducing the bug 1. I register for an event accepting the costs etc 2. The costs change 3. I pay more than what I accepted 4. I'm angry :angry: 5. Problems ### Expected behaviour Event prices cannot change after registration start! --- This is also important for #632, since payments are made using the price in the event and if the price changes the payments cannot reflect that.