The boot time is annoyance, and resource hogging is unfortunate, but I can easily buy my way out of those problems by buying bigger machines and doing it in advance. My time is more valuable, I think, and server costs are negligible next to payroll. There are business models where hardware costs dominate like, I don't know, video processing or something, but most startups are not in that boat - they need to iterate on UX as fast as possible.