I've bought lots of skis/bindings from the US to Canada (I live in Calgary).
Skis should run you $30-50 depending on UPS/Fedex/USPS/DHL. At least in Calgary, Fedex is by far the best in terms of service and brokerage fees.
What will happen is you will pay
a) Shipping to courier
b) Duty (maybe, if the stuff is new, you will pay duty for sure, if used/gift you might get away with it)
c) Brokerage fee (the fee the courier charges you for processing the paperwork with Canada Customs)
UPS are a bunch of assholes and rip you off charging ~$50 brokerage fee while Fedex has charged me $5-10 in the past (on $400 skis).
The "box" is included in the damn shipping/handling charge of $30-60US. This guy is an idiot, present him with the shipping quotes (I'd use Fedex or USPS) and if he insists on those charges dispute it with eBay. Make it clear you know he is overcharging (say you've bought stuff in the past for less).
Sometimes you get idiots on eBay who say they will sell within North America, and then are mad when a Canadian wins the auction (who knows why, they think it's a hassle for some reason) and try to screw you. Don't stand for it.