I have purchased knives from many US suppliers, both private and retail.
Many times the posted shipping cost is based on premium shipping options (fast with enhanced tracking). I find if you contact them, directly or via e-mail, they are often willing to provide lower cost shipping choices.
Keep in mind you lose some of the benefits.
Just last week I purchased a Kershaw Nakamura. The shipping cost with USPS was posted as $27.00 usd to Canada. I contacted the vendor and was quoted $8.00 usd shipping.
I opted for the low cost option. Tracking is basic, and I will be waiting 10-15 business days for delivery, but the cost was reasonable.
Kevin