The question is how much does a Boston Dynamics robot full of complex hydrolics cost vs a Tesla bot that full of electric actuators. Boston Dynamics robots aren't really design to be produced in numbers and are designed for a different use-case.
Boston Dynamics' humanoid robots thus far have been R&D platforms so the cost isn't all that important. That said, they released a quick teaser for the next gen of Atlas which seems to be all electric.
