Again, it varies a lot. I've seen dealer markups anywhere from 10% to 200% on those prices. There are a lot of nuances as well.
For example, I have one dealer who at this point probably has 100 facilities and 2000+ cameras deployed across the US for a remote monitoring application. Part of their contract to their end users is that if the system is down the dealer will deploy a guard, at their expense, on site until the system is repaired/operational again. With that many sites, and that much equipment, the odds are that you're going to have a couple of outages a year. In this case the markup from the monitoring cost includes some hedge for the "on site guard fund", almost an insurance of sorts.
In another situation, a dealer has cameras at very remote sites that get very minimal activity. There is no "we'll put a guard onsite" provision, or similar commitments. Just a very simple monitoring agreement. Those sites are roughly $200/mo. to the dealer, and they're charging the customer $250/mo. The central station doing the monitoring is handling the invoicing and billing, under the auspice of the dealer's brand/logo. In this case the dealer needs to do nothing other than cash their $50 "commission" check each month. I've also seen that same general setup where it's $200 to the dealer and $1000 to the customer. The dealer, who is completely passive in the month to month operations, is making significantly more profit than the monitoring center that is providing the actual service.