It is generally assumed that gathering more data is a good investment for conservation planning. However, the benefits of additional data have seldom been evaluated by analyzing the return on investment. If there are diminishing returns in terms of improved planning, then resources might be better directed toward other actions, depending on their relative costs and benefits. Our aim was to determine the return on investment from spending different amounts on survey data before undertaking a program of implementing new protected areas. We estimated how much protea data is obtained as a function of dollars invested in surveying. We then simulated incremental protection and loss of habitat to determine the benefit of investment in that data on the protection of proteas. We found that, after an investment of only US$100,000 (∼780,000 South Africa Rand [ZAR]), there was little increase in the effectiveness of conservation prioritizations, despite the full data set costing at least 25 times that amount.