I would be fine with them charging the same for SEA-YVR-X flights as for YVR-X, but I agree it's offensive for them to charge less for flights from the US, especially considering Canadian taxpayers paid for a lot of the infrastructure AC relies upon.
Ok fine, to be honest I find the entire idea of revenue management annoying. Just pick a damn price and charge me it already, bonus points of its related directly to your costs.