When people choose, they accept one alternative and give up another. Deciding to make no choice is a choice and has consequences. There will be consequences to students' decisions measured in class currency. They base it on how many weeks are left to factor in rent savings to themselves or potential rental earnings if they are purchasing it as rental property. They are making an informed choice and their choice does affect them and others.
People respond to incentives.
Students definitely will respond to being paid to come to class, not to mention having the opportunity to make money in other ways or even to win a prize at the end of the simulation. Voluntary exchange, both domestic and international, is a win-win situation for the traders. This simulation gives students the opportunity to conduct exchanges, transactions all on a voluntary basis. We know as rational individuals, that they would not enter into an exchange unless they anticipated a gain. In a market economy, prices identify how scarce one good or service is compared to other goods and services.