Originally Posted by
dc2447
The cost is £60 plus difference in flight cost apparently.
330 seems a lot from TXL => LHR mind
So not a fully flexible fare, then, but something which could have been as cheap as O class (€19 one-way plus TFC).
The fare difference between the O class one-way fare and the Y class one-way fare is about €581. So the fare difference you've been charged isn't extraordinary. It all depends on availability at the time of the change.