Standard commission is 10%, although that can vary based on the volume of business that your agency does with Disney.
Some agency owners or travel hosting companies take a percentage of that before passing on the money to the agent. This can vary from 20% to 50% to the agency, so the agent ends up with between 5% and 8% of the total booking.
Commissions can usually range between 5% and 15% from most suppliers, with the majority being at 10% - usually no commission nowadays from the airlines.
(my father owned an agency for a few years)
Don't forget to look at both sides of the coin - when you book that $49 room w/ tax ($55) at the All-Stars, this means the agency/agent gets $5.50! (the agent may only get $2.75 or $4.40, depending on their arrangement with the agency)