Comcast connections are metered for most residential users. Additional costs are incurred after 1TB of transfer. Also, home uplinks are generally pretty slow, and the VPN will be bottlenecked by its up speed.
you should be aware that VPN traffic still goes toward your 1TB data cap... actually, it probably uses a tiny more data then if you were not using a VPN...
I think cookiecaper read your earlier message as "why don't you run the VPN endpoint in your home" rather than "why use a VPN at all if you're going to put the endpoint at a cloud service".