Yep. For the ones I've looked into, orders match when they sum to $1. Eg, I bid $0.75 on yes and you bid $0.25 on no. The contracts are very carefully written s

Yep. For the ones I've looked into, orders match when they sum to $1. Eg, I bid $0.75 on yes and you bid $0.25 on no. The contracts are very carefully written such that they are mutually exclusive, only one of us gets $1 when the contract resolves. And like you suggest, you pay a fee on the way out.