Well, models generally rely on parameter values which can be determined empirically or reasoned about more theoretically or the model could be fitted to data and the parameters inferred by some form of optimisation algo such as monte carlo markov chains.
Anyway, suppose two people disagree on the value of a parameter. Running the model with different parameter values would produce different predictions, which they could then bet on.
Well, models generally rely on parameter values which can be determined empirically or reasoned about more theoretically or the model could be fitted to data and the parameters inferred by some form of optimisation algo such as monte carlo markov chains.
Anyway, suppose two people disagree on the value of a parameter. Running the model with different parameter values would produce different predictions, which they could then bet on.