I think it's the shows. My buddy does all the behind the scenes stuff for some of these huge music shows. He said he thought DJ's made a lot until he saw what some of these hip hop guys were getting. He said Drake was getting 2 million for 1 show and acts like lil yachty or whatever his name is was getting like 300k for an hour show at one of these festivals.
Little bit from streaming/sales, huge bit from touring, plus a varying amount from being an internet taste maker.
For instance, Tekashi was around $12 - 15,000 when he started to get hot, peaked at around $40,000, and now is around $25,000, but he isn't getting booked much now because of all this gang shit. That was the fee for larger shows.
I remember fees for this XXXTentacion kid being in the high 4 figures, low 5's a few years ago, and he was selling out decent sixed clubs at $25 - 40 a ticket.
So there is huge money in touring.