I once had a return ticket to fly on Virgin Airlines for a domestic travel journey. This was probably around four years ago now. The flights were cheap, so there were no cancellations allowed. Before making the return journey I had to change the booking. The price to change the ticket to a different flight was horrific. I ended up just buying a new discounted ticket instead which was cheaper than the rebooking fee on the other ticket, even after factoring in the price lost on the abandoned return flight.