It's only fair
Something you say to comfirm two completly unfair things as fair.
He stomped on my toe so i kicked him in the nuts, it's only fair.
And that can only be fair play to ya!
another way of saying "well done" or "fair play to ya" except funnier. A preferred term among Football managers.
“Andy Reid, you have lost eight kilos and worked extremely hard and that can only be fair play to ya!"