You need to know the market value of the house

Usually the agent can find the price of the most recent sales, seller's subsides, ect., of the comparibles to decide if the target house is a good deal or not. It is hard for a buyer to make such decision without such assistance.

For me, I usually know the market better than the agents, so it makes no differnece.

In addition, you may want request further price reduction as the seller saved the commission.