I booked a multi-stop open jaw with them on LH. I needed to change the date of the last leg. Called them and they quoted me $300 airline penalty, $150 justfly penalty, $300 fare difference and taxes of $60.23. This basically made it cheaper for me to buy a new ticket for the last leg on another airline.

Just to check I called LH directly and they made the change for $300. No extra fare difference or tax. Remains to be seen if I'll get charged another $150 somehow but if I do I can guarantee I'll never use them again.