Hello good question! Many buyers think that if they go straight to the source, in this case a developer they will do better than working through an agency. This unfortunately is not true.
Most recently with my experience, I was able to negotiate a price $18,000 less than the price they told my buyers was their bottom price at a Toll Brothers property in Hoboken. I was able to provide Toll with some research and we negotiated successfully.
Not only can an agent negotiate on your behalf the best price, they are in the know about any pit falls, or perks that could be shared with you.
Hope this helps! And remember, working with a real estate agent doesn't cost you anything. On the contrary, it saves you money.