While checking prices on the Emerald cruise I booked for next summer, I discovered a number of online TA's offering the same cabin for about $400 less. I contacted my TA who told me about a 3-day sale going on with Princess, which ends tomorrow. She re-booked me at the lower rate and I was able to keep the same cabin and the OBC I had. It pays to regularly monitor the rates.
You have made an excellent point. After booking any cruise I always watch the Internet for any price drops. I usually book direct with the cruise line, but even if you are booked through a TA, at the end of the day, it is always your responsibility to watch for those price drops.
Have a great cruise.
With integrity nothing else matters; without it nothing else matters.