The only way to find it out is to get to play with MK on tour, but your contract will probably say to never talk about money
With that said, here in Russia as far as I know, a touring musician for a famous artist can easily make as much as a median month salary for each show, like $1-2 grand for a show.
So mathematically speaking, touring musicians aren't the wealthiest guys in the world, but man they certainly are the luckiest, especially if it's a major tour with jets and such.
UPD: the difference between the artist's salary and the musician is something like 50:1, so the artist's salary is 30-50 times more than this of a regular musician.
And you have to think that they don't have a salary for granted...
Musicians like Bennett, Worf, they work very frequently, but others maybe work once or twice per month, so even you get paid more than a regular worker, the amount of time you work doesn't makes you get more money than a regular worker.
I know a bassist and a drummer who play with some of the biggest musicians in Spain, and I mean BIGGEST really, and in between their records and tours, they don't have much work so they have to save money from the good times to live the rest of the time they don't get calls...