According to the Cornell University study,

Keystone XL will increase the price of heavy crude oil in the Midwest by almost $2 to $4 billion annually, and escalating for several years. It will do this by diverting major volumes of tar sands oil now supplying the Midwest refineries, so it can be sold at higher prices to the Gulf Coast and export markets. As a result, consumers in the Midwest could be paying 10 to 20 cents more per gallon for gasoline and diesel fuel, adding up to $5 billion to the annual U.S. fuel bill.


[link to www.usnews.com]