I do not know the cost for the Keystone, but the Northern Gateway is proposed at $5.5B. Kestone is about three times of the length of Gateway, so it is a $15B project.
The construction will need a lot of people, but once it is built, the service stations will need a lot fewer people.
The proposal for the Gateway says that the people along the line has 10% ownership of the pipeline, that is huge for doing nothing, and they will benefit for the lifetime of the pipe and maybe forever.