The in-person prize pool, where the first person to hit the legend rank or the highest ranked player at the arena after 24 hours will get the in-person bonus of $10,000. There will be random events and things occurring to players to spice things up throughout the 24 hours at the arena.
All $10 of the entry fee goes directly to the online prize pool which is paid out in full. The online prize pool, which is crowdfunded through Matcherino, goes to the first 3 players who hit the legend rank online or in-person.
Hunterace used this Razakus Priest list to hit Legend and got first place for the Online portion of Rat Race. Check out the stats on his run here. Amnesiac was the winner of the on-site/invite portion of Rat Race.