This is super cool. Private runners are often so much cheaper, especially in large teams. Comes with a "fat tail" of reliability risk though: taking maintenance of runners means that that say 0.01% of builds would be failing for unknown reasons and it'd take significant effort to fix those. But then again that'd probably be only relevant in large organisations which likely have bigger bottlenecks in their devops practice than that; and if that's just about cost then a no-brainer.