Its not what he’ll charge that’s important, its what price for the property he can get that is.
I agreed a deal with ours (2 months ago); he said what he could get and his fee. So I offered a lower fee for that price and his fee for the price + £10k. If he got more that the £10k extra I said he could have 10% of any additional.
We sold within the week, at just over 110% of the original thought – maximum really as this hit the stamp duty level. He got more, I got far more – all happy, and they worked for it too, as they knew they could make more money.