This paper investigates the impact of monetary rewards on behavioral strategies and the quality of posts in consumer generated media (CGM). In recent years, some CGM platforms have introduced monetary rewards as an incentive to encourage users to post articles. However, the impact of monetary rewards on users has not been sufficiently clarified. Therefore, to investigate the impact of monetary rewards, we extend the SNS-norms game, which models SNSs based on the evolutionary game theory, by incorporating the model of monetary rewards, the users’ preferences for them, and their efforts for article quality. The results of the experiments on several types of networks indicate that monetary rewards promote posting articles but significantly reduce the article quality. Particularly, when the value of the monetary reward is small, it significantly reduces the utilities of all the users owing to a decrease in quality. We also found that individual user preferences for monetary rewards had a clear difference in their behavior.