The only way the price should vary from TA to TA is if one is holding group space. If that's the case, if you are booked into group space, you cannot apply the Amex Plat benefits. I am 100% positive on this. Royal used to let it slide, but they've become very strict on it over at least the last year. So if the Plat Amex benefits are important to you, look at your confirmation to see if you have a Group ID on it (at the top following your confirmation/reservation number). If you do, Royal will not add the Amex benefits. If anyone says yes they will, that person got lucky and got an inexperienced cruise line res agent who didn't know policy or simply made a mistake. This is specific to Royal, not other cruise lines. On Celebrity, for ex, you can combine it with group rates.