It's difficult to tell who is the richest because making money from live shows is one thing, but turning that money into wealth is another.
A recording artist can be paid good money for a show and spend that money recklessly on drugs and women while another artist can be paid peanuts but through investing they can make it worthwhile in the long run because investing is a marathon, not a 100m dash.
For those above-stated reasons, this is why I personally think that without going through the income statements and tax returns of these artists it is just mere speculation to say this artist has more money than that artist.