If a dealer doesn't make money on the stuff he buys, he doesn't stay in business. His markup needs to be at a level that will keep the lights on, employees paid, and the doors open.
The longer stuff sits on his shelf, the more money it costs him, and there is a limited market for LF and ULF gear, especially ULF.
Generally speaking, in the buying and selling of used stuff arena, the larger the lot, the less money per item. Another rule of thumb is that the retail price of a single piece of the lot should be enough to fund the lot price. The reason is that it make take years to sell the rest of it.
If you anticipate a problem selling all the stuff, a dealer will have the same problem. To get the best price from a dealer you'll need to sell in small quantities, maybe one or two cameras at a time.
If you need to get the best return you can quickly, the best choice might be a local auction. If you have some time available, and you can transport the gear, you might consider tables at some of the camera shows, or try contacting and orgainziation like PHSNE to see about including the gear in their auctions.