First off just because they have an estimate of that much doesn't mean they get all that money. Riot has been bought from Tencent. I'm sure most of the income goes directly to them and then branch out to the different LoL HQ around the world.
Also note that I would assume majority of their actual incomes goes to E-Sports. Look at the venues/stadiums they rent out to play at these. Those aren't cheap and I doubt the owner of the stadium is giving it to them for free. With usually tournaments running a month long that will probably eat up a chunk of that income. Now you also need to take into account all the peoples plane/hotel tickets that need to be there: pro players, managers, host/shout casters, riot employees, tech people, merch dealers, etc. it's crazy how far they go for these events when oh have people disconnecting from your game because of your servers, or other reasons not related to the players.
It's horrible where their priorities lie when it comes to this game. But they made it their choice to make E-Sports a thing, and while I disagree, I know the community/fanbase does like this sort of thing. If people keep attending these events they are going to take advantage of that. So of course they will keep improving and spending hundreds/thousands of dollars just for these events.
