You pay custom duties ONLY on items purchased outside the US if you are a US citizen. Canada will not colect duties from US citizens entering Canada unless you intend to bring items into Canada for personal permanent use. If you purchased a refrigerator in the US and brought it into Canada for your Canadian vacation home, you would probably be liable for Canadian taxes.
Correct me if I am wrong, Kuki, please. My sister and brother-in-law have a cabin in northern Ontario and they have been assessed duty on items they have "imported" from the US.
If your purchase merchandise in Alaska, as you describe, there should be no duties applicable. Note I use the word :"should". Merchandise purchased in Canada exceeding your $400 per person limit couldbe liuble for custom fees.
I recommend that you get a free booklet from the U.S. Custom Service entitled "Know Before You Go" Mail:Custom Department of Treasury, U.S. Custom Service, Washinton DC 20229 or you can go on the WEB for a print out of Know Before You Go. You can download it and it prints out 22 pages,