> increasing yellow light duration is significantly cheaper than contracting out a network of cameras to a vendor who takes over half the revenue from each ticket.

It's cheaper for society, yes. It's much more expensive if you're the government notionally "paying" for that contract. It's paid out of revenues you didn't have before.

Ever time I've ever heard of these being implemented, the company selling them provides the cameras and installation at no cost. That's how they justify collecting a cut. It's free money for the city.