Definition
This phrase is used to indicate that an offer or arrangement is considered very reasonable and cannot be improved further.
待遇很好，公平合理
This price is already very fair for you; you can't ask for more. You can't say fairer than that.
这个价格对你来说已经很公平了；你不能要求更多了。你无法找到比这更公平的了。
I'm willing to pay half the cost; you can't say fairer than that.
我愿意支付一半的费用；你无法找到比这更公平的了。
She's given you this much time to complete it; you can't say fairer than that.
她给了你这么多时间来完成它；你无法找到比这更公平的了。