Tell them you will pay 5%, take it or leave it.
I met with several realtors hear in Texas the past couple of weeks. All want an "exclusive right to sell" and claim that 6% is "customary". Of course they will also claim that they have no agreement with other brokers regarding the 6%, it's just "customary" whatever the heck that means. Frankly, I wonder if they are violating the Sherman Anti-trust Act with that statement.
But it sure make me feel good knowing that at least they are "ethical".