When was this ticket booked, and what was your status at that time?

sounds like this matches the fees for a silver before the last set of changes in Oct. - and tickets booked prior to then should be subject to the old fees. For changes >21 days in advance, free for silver, or $125 to redeposit. That seems to match what you are seeing - though fees are supposed to be based on status at the time of the change.