Prizes seem like they could be a natural fit with the ARPA Model, yet DARPA doesn’t seem to use prizes outside of a few competitions like the DARPA Grand Challenges and Robotics Challenges. Specifically, prizes seem like they’re just one more path along the theme of Top down problems and bottom up solutions beyond open solicitations and parallel efforts. IARPA’s heavy use of competitions suggests that there is merit to the question. One prize-dissuading possibility could be that most DARPA projects are more capital-heavy than IARPA’s mostly computer-based-projects and capital requirements would make people hesitant to work towards an uncertain payout. Another possibility is simply tradition and government rules. It’s worth knowing whether it’s the former, the latter, or something else if you’re going to riff on the ARPA Model.