I am totally pushing for guests to book wiht our TA because we DO get comp nights plus a bunch of other free stuff the more rooms in our group block! The way I approach it is that althoiugh they could book on their own, there are no guarantees that it will be the same price, or cheaper and then they have to worry about the added headache of taxes, gratuities and round trip transfers to the resort and back to the airport, seems like the cost would be a BIG motivating factor for people