That's right, I realized the only reason he would get a refund is if he had paid in full before the final payment is due...
Banshee...
In case you do not know, there will come a point, probably about 90 days before your sail date, when you will have a set price (there may be even more adjustments before then) but at that date - when "FINAL PAYMENT IS DUE" at that point the price will be locked in for you - and any further price changes will NOT result in any benefit for you.
That is - unless the cruise line or your agent decides to make up the difference somehow with an onboard credit just out of kindness (I have heard of this happening) - however, technically and contractually they will not owe you anything after that point.