What should be my budget for a high-end gaming laptop in UK?

Hi, It is my first question which I have asked in the title. Actually my son want to play high-end games. I suggested a desktop PC but he would like to go with a laptop. Now I am confuse as I am not aware about gaming laptops and that’s why I decided to visit here . Now kindly give me an idea that how much my budget should be to buy high-end laptop and if you also know about any gaming laptop, then also share as well.