- Concept
You want the tournament to be original. 2v2, 1v1. Clans only? For which division or maybe for all? If it is for all skills, what seeding method are you going to use to make it more fair?
- Rules
Looking at the state of the game - what is considered OP? What needs to be banned in order for everyone to have a fair match? Mirror matches allowed in the qualifiers? Best of 1 or 3?
- Artwork
This is the ultimate time consumer. Logo's, twitch scenes, highlights, little things like paragraphe-dividers in your newspost, overlays, intro videos, and tons of artwork I am not even mentioning. Photoshop and Illustrator hours x 100000
- Videos
Intro vids, background vids, VODs on YouTube, worldbuilder mapvideos, ..
Sony Vegas x 100000
- Prizes
The hunt for good prizes cause you want the players to fight for something. This can be a pain in the ass cause as organisor you are already putting so much work in a tourney where you gain absolutely nothing. And now people expect you to have money/hardware prizes? That's absurd, but the show must go on.
- Streaming
As mentioned before artwork, setting up Obs (scenes, hotkeys, testing, scources,... ), buying proper mic and webcam, buying a good rig so you can stream HQ, ...
- Creating newspost
Writing everything out in a well written post (which most of the players don't even read).
- Managing sign-ups and creating brackets + seeding
Who's playing against who? Randomization, cointoss or the referee decides who plays against who?
- Tourney day
No-shows, managing problems, timezone issues, people being late, people who has not read the rules or timetable,..
- Streaming live
After setting it up, you have to cast all games. Its super time consuming.
- A lot more details I'm not even mentioning.
You should know that many of us work on all of these things said above for FREE. We put in effort after we have gone working for a whole day.
What I am trying to say is - apart from the site management itself (I do not have knowledge about that) - tournament organisation itself is a HUGE effort where you gain absolutely nothing as organizer. With both Rewind and One4One I have gained absolutely 0 money. And I believe ThightRope, Romeo, Ipkai and more also gained nothing. So it is normal that the admins of such a large community receive something after years and years of site management and organisation.
Is 50% too much? Well I leave that up to each individual. I don't think it's right to compare it to huge DOTA events though, as there is a lot more to be paid for and does not run on donations. But that said, Ami has always been transparend about 50% - 50%, so there's not much you can say about that.
Hopefully you have more of an image what it takes to make and hold tournaments.