Browser engineers aren't exactly cheap. 250k for a good C++ Dev is reasonable. Assuming 100 engineers (a very conservative estimate), that's 25 million in just pay alone. 50 million including codec. Now add in the costs of infrastructure, community engagement, DevOps, Marketing etc. and the costs will quickly balloon. Browsers are critical infrastructure like operating systems. Their complexity is on the same level as OSes, perhaps even more. It's exposed to hostile code everyday, you don't want people who don't know what they are doing to work on it. This isn't some sort of dating app where the only vulnerability you have to worry about is a code injection in the birthday form field.