Combine Cloud9 with a $300 touchscreen Chromebook and that's a hell of an environment vs buying a $2000 Macbook.
edit: This bit is interesting though: If you’re running in AWS the auto-hibernate feature will stop your instance shortly after you stop using your IDE. This can be a huge cost savings over running a more permanent developer desktop.
So perhaps the cost is quite a bit lower.
But sure, if that is your life, or your very strict work life, I guess it can work fine. Would never be able to work for me since I tinker with so much random shit.
Cloud9 isn't the only cloud dev environment out there.