Adding to that, there are some times when a TA can discount a cruise, but not post the discounted price due to restrictions by the cruise line. As an example, we once found on our TA's website 3 cruises to Alaska that met our desired time frame and ports. When I called him, the one with the highest price on the website ended up being the one with the lowest price.
If you are going to book with a TA, so it over the phone, not online. That also allows you to ask whatever questions you want to ask.