OK. This time I saw the announcement you are quoting. I did not see that before. What I was referring to was in the "Competitive Advantage" chart where if specifically says:
Cruise Single Supplement: $695. FREE Single Supplement on optional extensions
So there is an inconsistency between pages of the web site. But based on what Pauline pointed out, added to the "low price guarantee" I would think that the full refund should be offered. To me, the low price guarantee should apply to GCT's own price changes as well as that offered by competitive companies.
To offer a precedent: A few years ago I saw a tour that I had already paid for being offered by GCT for $600 less than what I paid. I requested and was given a $600 refund. I received, not a credit, but an actual funds transfer to my checking account to offset the electronic funds transfer I had used for the payment.
I'm sure that "legal" arguments could be made that our cases were not the same, but it would seem to me that the "ethical" arguments would support the refund.