not because you don't have an agent.
99% builder will NOT lower your price by additional 3% just because you don't have an agent.But they will be happy to make you think that way.
If you go to sales office alone first time, and you don't know whether you will have an agent or not, do not give sales any information. Not even your name. If agent ask you, just tell him/her you want to get some information for your relative. Do not try to bargain price without sufficient research.