The less you tell the agent the better about your situation, why your moving or selling. Keep it a pure business discussion. In theory you should interview 2 or 3 with their market evaluations. Or better hire a bank appraiser to get you a realistic price. Some realtors will say anything to get a listing. I would shoot for 4%, you may end up paying 5%. They are all shysters.
Can't say I disagree. On an expensive house the broker WILL dicker on commission. Watch out for the old game of giving you a high estimate of the sales price and just to get the listing and then the grind down where you swear the agent is working for the buyer instead of for you.
A big reduction in sales price doesn't mean a big hit on commission and a lot of the big talking, fancy (leased) car driving "agents" are swinging from sale to sale, and are broke in between. I once saw a big talker get her Benz snatched by a repo guy right at a closing.
When you're buying a new house, there's nothing your agent likes to hear more than that your old house is under contract and you have to get out. Then you become one of the folks who can be force fed almost anything.
You should find out what the ethics requirements (LOL) are for agents in your state. Specifically, who IS "your" agent working for... you, the other party, or his or her firm, especially when there is only ONE agent involved. You might be surprised at the answer.