That's terrible on US / Canada postage rates & duties.
I hope it is temporary.

For selling FROM Canada TO USA, particularly with eBay involved, it is crushing.

For selling FROM USA to Canada, if person-to-person (not eBay), there's a USA based discount service called PirateShip.com

https://www.pirateship.com/rates

Others have been using it for some time with good results (and noticeable savings!) vs. USPS rates. (I'm late to the party, but coming around. It DOES save money on packages vs. taking to the local post office to mail.

If you're BUYING from individual sellers or websites here in the US, you might ask them to check out PirateShip.com. It's a win-win for both.

As an example, I check price for mailing a 5 x 8 inch soft (padded) envelope at 12 oz. weight. (You could get lots of chips in that.) Their price, via UPS Standard, is $16.64 from my zip code, shipping to Canada, with estimated 5 days door-to-door.

I should have mentioned, they work with UPS as well as USPS (our post office). Their cheapest USPS quote for First Class International Package is $24.69.

I'm not sure how custom / duty declarations or fees work on such a shipment.

Just some ideas. We like our Canadian chippers in the CCA -- Sean, didn't we work together at the club Promotions table in June? -- so hang in there, eh?