It's not a scam it's just slightly shady.
This is basically how EVERY shipping company works (Post Offices not included). In the fine print any charges the consignee does not pay will be charged back to the shipper.
Of course most companies would rather collect the money on the spot and avoid the hassle but UPS is not one of them. They generally don't even inform the recipient at delivery that an additional charge will be billed later.
When shipping International via UPS or FedEx it's best to include the brokerage charge in your handling total and send the package "free domicile" (all charges billed to shipper). I'm not really sure what the situation is with duties and taxes you may need to find out about these as well to be completely covered.
The easiest solution is to only ship via Canada Post, only ship under $200 (UPS Ground to USA is has no brokerage charge if value under US$200) or use something like FedEx Premium service where the brokerage charges are included (I think UPS Express is also that way).
Ben

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
- answering Trolls is voluntary, my policy is not to participate.