Yeah I agree with not taking people's word for it part...I just think that the 10k thing is a bit like the old poker adage of position in poker being like water: you don't need to know why it's good for you, it just is. There are other things you should probably spend time thinking about.

Enough mathematically savvy players will have bandied that number around for us to trust that it's somewhat reliable, or certainly enough for bustostakes.