In Pelota matches, bets are made between viewers through a middleman who receives 16% of the finally paid amount. In this paper, a description of the way bets are made and an explanation of the existence of those markets are presented. Taking betting markets as a simplified analogy for financial markets we have searched for the explanation in a world where both sides of the market are not different in believes and preferences. We find that for a bet to exist (...) when bettors are rank dependent expected utility maximizers, they have to be optimistic. Taking observations from actually made bets a preliminary analysis about the biases of those markets is presented. (shrink)