To be honest I would rightly or wrongly assume that they do get commission but I wouldn't say it was from your hotel bookings more like on the actual components of the wedding itself i.e. which location you went for and the mere fact that the minimum would have to be $7,500 or $10,00 depending on which day of the week you booked on.
Certainly if this was the case my SM would have taken a loss as after their first quotes to me on the hotel rooms I was not a happy bunny on the moderate hotel rate that was given to me and basically told them - my SM then came back to me the next day with a better rate.
That said to be honest I wouldn't care what commission my SM got and where it came from as it's not really my business. I was happy with the service and I was happy with the rates finally quoted to me and when I wasn't I made sure they knew about it and they did what they could to make my wallet smile a little more.
Louisa I'm not sure why you ask the question but reading some of your previous posts if you are not happy with the service you are getting from your SM you really need to address this with their supervisor or just try and get your SM changed