In defense of dealers;
Some dealers, (and private buyers) will low-ball. But, others will give a fair-market price.
Since by definition, a dealer will be re-selling, and therefore buy at wholesale prices; the mark up needs to cover the expenses of purchase/transport/prep for sale/rent for the shop/electricity/insurance/wages for any employees, etc.
Then, some of the items will sell quickly, and make back their cost, others will sit on the shelf consuming shop resources, and may never sell, or when they do, it may be a net loss. The mark-up needs to cover that too, or else yet another camera shop will be seen closing up and going out of business.
When you sell to a dealer, you gain convenience, and save yourself the time and effort to research and prep each item for sale, but no, it won't yield the best possible price. Everyone's time has a price though, if the time spent in marketing the stuff is more productive for you doing something else, then selling to a reputable dealer may be a good option. In between, a well run auction is probably the best option for time invested vs. money gained.