Cost of building is a true concern, but it doesn't stop people from forking large open projects like Chrome or Firefox and try to build a project to pursue their own ideas and be able to contribute back to the upstream projects when it makes sense.

I don't build my browser, it's too expensive, but the cost of building has nothing to say with how open the access to things. It'd be cool if the community could fork the project, propose changes and maybe crowdfund a training/build run to experiment.