It's highly location dependent, but the most common pricing structure I'm aware of is $25 a month for straight monitoring, $30-$35 a month if you throw in some kind of service agreement for the equipment, and up to $50 a month if you provide the equipment free. There's all sorts of services you can add-on, like open-and-close reporting, environmental monitoring, etc etc etc. In reality, these are basically pure profit, as monitoring usually costs you, the dealer, as little as $3-$5 a month per account if you guarantee the central a specific amount of sign-ups per month.
If you decide to sell your accounts as soon as you get them, of course, the dealer program will have some guidance as to how much to charge beyond just "as much as possible".
But ask around to find out what your competitors are charging, because you don't want to charge significantly less than what the market will bear.