Recent work on hedge fund activism documents substantial abnormal returns but fails to answer the question whether these returns cover the large costs of activist campaigns. This paper provides benchmarks for monitoring costs and evaluates the net returns to activism. I model activism as a sequential decision process consisting of demand negotiations, board representation and proxy contest and estimate the costs of each distinct stage. A campaign ending in a proxy fight has average costs of $10.71 million. The proxy contest is the most expensive stage, followed by demand negotiations. The estimated monitoring costs consume more than two-thirds of gross activist returns implying that the net returns to activism are significantly lower than previously thought. Even though the mean net return is close to zero, the top quartile of activists earn higher returns on their activist holdings than on their non-activist investments.