I think there is perhaps one other angle of this that has not been mentioned.

One theory going around is that this also helps the cruise lines as well as the
"regular" travel agents. In other words, if the lines allowed the biggest of
the big to gobble up most of the market, the few remaining mega-monster
agencies would end up dictating terms to the lines, not the other way around.
That would be bad for the lines, and with reduced revenue, bad for passengers
(note "passengers", not "guests", but that is another discussion). Reduced
revenue, if reduced too low, means reduced quality onboard - food and staff
levels being obvious reductions. Ticket prices too low = something has to
give.

As a T/A, this is not the sky falling. And it is still legal to rebate (we
don't for good reasons, but our business model may not be for everybody). You
just can't advertise that. You can offer subtle hints that are generalized and
not specific (i.e. call for our best pricing, versus call us to get lower
pricing on this RCI cruise).

Regards, Keith