I just changed a return on a WFP + MFU (inflexible) for a mere E 150,-. At first they quoted me a much higher change fee, but I just thanked them politely and called back to get my desired response. They did tell me that once you have flown the outbound a date change actually becomes cheaper since they do not reissue the ticket, thus preventing that you end up in higher fare buckets. They granted me that fee as an exception (ie before flying the outbound) and said something about me being a God.
Or Gold. Can't remember.