The problem I see with those proposed player-sponsored tourneys is that WGT would actually have to open their books to members and players.
It's not just the 10,000 credits. It's the additional advertising dollars that WGT is charging the sponsors and keeping as profit margin that I'm sure they don't want broadcasted all over this site. They could be charging the equivalent of 10,000,000 credits and only offering 10,000 as prizes. They are not going to want that to be general knowledge.
They could also be claiming 5,000,000 registered players but admitting to sponsors that 4,500,000 of those accounts are inactive or multiple accounts in order to avoid being run up on fraud charges. Think of what these forums would look like if that became common knowledge.