Seems to be a combination of cost-of-living and demand. Consider the following cost-of-living comparison between Vancouver and Seattle: Consumer Prices in Seat

Seems to be a combination of cost-of-living and demand. Consider the following cost-of-living comparison between Vancouver and Seattle: Consumer Prices in Seattle, WA are 20.02% higher than in Vancouver Consumer Prices Including Rent in Seattle, WA are 22.54% higher than in Vancouver Rent Prices in Seattle, WA are 26.38% higher than in Vancouver Restaurant Prices in Seattle, WA are 19.51% higher than in Vancouver Groceries Prices in Seattle, WA are 21.84% higher than in Vancouver (https://www.numbeo.com/cost-of-living/comparison.jsp https://www.numbeo.com/cost-of-living/comparison.jsp)