Where does the 10% or 15% go?

Good question. In a nutshell: things cost money, and people are spending a lot of time organizing and setting things up to host these events.

For Local events, half goes to the local tournament organizer/director: posters, their time, and other costs... or how ever they decide to break it down (Shirt for the winner, plaque/Trophies etc) and the other half to MLD: which pays for, paypal and credit card fees, web hosting, domain names, banners, use of logo, Tournament Computer Program, etc.