I've suggested this as well, but none of the Keystone proponents here has been up to addressing it. I finally decided to do a little digging, and found that Keystone, itself, studied this impact. They reported that due to excess regional capacity, they must currently discount oil by about $3.24 per barrel when selling to refineries in the upper Midwest. This costs them up to $3.9 billion per year compared to the expected export profit once Keystone XL is built. This will be coming out of consumers' pockets throughout the upper Midwest. That's the modern GOP, bending over working Americans once again.
Here's the report:
https://docs.neb-one.gc.ca/ll-eng/l...sons_for_Decision.pdf?nodeid=604637&vernum=-2
This shouldn't really be a surprise to anyone who understands basic economics. The Keystone XL project is expected to cost around $7 billion. (I strongly suspect that does not include the lobbying costs that have lured so many politicians on board.) Companies don't spend that kind of money without expecting a significant return on that investment. Clearly, this is one of the ways they expect to recoup that cost, by increasing energy costs to millions of Americans.
Edit: For those interested in a counterpoint to the deceptive Perryman study, here's the study I was reading that led me to the report linked above:
https://www.ilr.cornell.edu/sites/ilr.cornell.edu/files/GLI_keystoneXL_Reportpdf.pdf . No doubt it has its own biases, but they document their work in some detail.