Since 2009 we've always booked our cruises through Costco (5 Royal Caribbean and 1 DCL). Costco is really great to work with. Like someone else said, you get OBC with RCCL and if you don't use it is is returned to you). We are going on Allure in a couple weeks and were able to get a fantastic package deal -- soda package for each person in the cabin, a specialty dining credit for each person in the cabin, floating mats at Labadee, a beverage credit on Labadee, one spa credit, access to the special play area on Labadee, a meal at Jonny Rockets
.. Maybe something else too, but I forget
..
This package was only supposed to be for the cruise the last week in February, but that cruise got cancelled due to Allure having to go into unscheduled dry dock. So Costco allowed us to still get the package at the sailing a couple weeks prior. RCCL was also giving people additional OBC for the hassle of the rescheduled cruise. Suites were supposed to get more than normal balcony rooms, and the "fine print" never clarified that Jr. Suites were not considered a "suite" for the OBC compensation. (The fine print always clarifies that a Jr. Suite is not a true suite!) We have a junior suite, so DH asked the lady at Costco travel if we'd be able to get the same OBC as the big suites (we originally were only given the balcony OBC). She went to bat for us and got us the higher OBC.
Everyone we talk to at Costco is always super friendly and helpful!
Travel agents aren't allowed to make the cruises cheaper than what you would get them straight through RCCL/DCL/etc, which is why they offer the extra incentives!