[jimworcs]

When you booked first class, do you happen to know what the cost of a economy flight was for the same booking? To suggest that the difference is only $52, the airline must have compared the cost of a full price economy ticket against first class. That is a false comparison. They should have compared what the cost of an economy ticket, purchased at the time your bought your original ticket would have cost. That would have been considerably less and the difference in price would then have been much more. Reject their offer and consider Small Claims Court. However, bear in mind that you did travel first class in 3 out of 4 sectors.