Try to follow this:

Booked trip from ORD to SNG in Mar05 for $900. Trip cancelled -- got a voucher for the unused ticket

Used voucher for trip from ORD to LHR and AMS to ORD. Price was an increase so I paid $270 increase in fee. Trip was scheduled for Jun06, but I cancelled.

Reschedule trip for Aug06 ORD to LHR (and back). Listed fare was ~$200 cheaper than what I paid for the previous trip.

UAL tells me that to rebook the trip the 3rd time I have to pay a $200 rebooking fee.

Did I just get robbed?