Cant help with pricing, but make sure the buyer knows that they will need a converter to use the UK power supply in Canada.
You can alway chop the plug off and put a new plug on . Thats what I do. BUT DO NOT DO IT ON A SLIM AS THE POWERBRICK GOES BANG.
Well I had an XNA kit and PSU shipped from Germany to the UK recently. The seller charged 35 Euro for the shipping via DHL and the box says that the weight is 5kg.
Try checking the price with surface mail if whoever you are sending to isn't in a hurry, it's way cheaper but can take about 3 months! Other than that check prices with Parcel2Go etc. Shipping is not cheap from the UK to here.