Hi there,
I truly believe you are crazy if you don't have at the least a book now button on your own webiste. It is a very minimal cost and definitely worth it. As for the other sites, yes you do pay on average 12% commission, but again, you really would be silly if you weren't at least on booking.com or wotif. With the amount of advertising they are doing now, you will miss out. We are planning on joing a few more sites in the next few days.