I'd keep pushing it. Last year we had booked a balcony on Princess a year in advance of our cruise. The price dropped $150/pp. I called Princess and they adjusted the fare. I hadn't paid for the cruise in full. If I had, they would have issued me an on board credit. Keep trying until you find someone that will make this right for you!
Penny, you had the price adjusted by PCL because it was not in penalty which begins at the final payment due date. HAL and PCL and others opperate the same when it comes to adjustments after the penalty period begins. They do not typically make any adjustments to fares or offer onboard credits, upgrades or any other considerations. There are a few lines that do work with you even inside penalty, Carnival, RCI and Celeb are the best about offering upgrades or credits if a rate drops inside penalty. They way they justify it often as Sandy says, "that's not the same category you booked". If it is the same Cat there is a whole bag full of other reasons (excuses) offered... "This promotion is a special promotion, for new bookings only". All PCL rates offered after penalty and most HAL are listed specifically as for new bookings only.
When you do actually reach a manager at the cruiselines the response is worded differently but always the same result. One once asked me if I bought a sweater for the winter season and it went down when the clearance sales started at the end of the season, would I expect the difference to be refunded? Great way to word it but in my opinion the season isn't over on a cruise until you disembark.
Happy sailing, Neil