The root issue is clearly NPM's terrible performance, but it seems to have been exacerbated here by VirtualBox's terrible networking.
Given that you're talking about developer environments, wouldn't it have been simpler to just try a different virtualisation tool like Parallels, VMWare or (if you're on Windows) Hyper-V ?
Given that you're talking about developer environments, wouldn't it have been simpler to just try a different virtualisation tool like Parallels, VMWare or (if you're on Windows) Hyper-V ?