In order to register to compete:

http://meetup.flyingrobotsnyc.com/events/80971122/

We’re going to limit the number of competitors to 10. To prevent signup flakes, people who sign up and don’t compete, while taking up a spot that an actual competitor could have used, we are charging a “flake-prevention fee”. In order to register you will have to pay $50. If you show up and compete, that fee will be refunded.

In other words, it is free to compete, but to register to compete without competing costs $50.

In order to register to spectate:

http://meetup.flyingrobotsnyc.com/events/78765472/

There is no fee to spectate.