Tariff for used item from Canada to US

I bought a used Auralic streamer from Canadian Audiomart, got a UPS email holding the item and demanding $450 tariff. I emailed the seller, an audio shop in Canada if I could have it returned, and they said no. I paid through PayPal. The shop did mentioned it MIGHT got tariffed since its a Chinese made item. Is it fare that they refuse to take back? What would you do if you re in my shoes? The $450 tariff will make it as expensive as new in US.
If I interpret your post correctly here’s my take :
The dealer told you on the front end that you had the tariff risk . Despite that you made the purchase and accepted that risk without doing some research beforehand on what the estimated tariff might be. So yes, I think it is fair that they don’t take it back you made the purchase knowing there was the risk,  the fact that you didn’t look into the risk before agreeing to the purchase isn’t their fault.
I am at a loss to understand this.  I am in the US.  For many years I have been buying electronic (and other) merchandise from foreign countries. Among these 2 cartridges, a DAC, connectors.  They have come mostly from Asia, but also from Canada and Europe.  About 5 months ago I bought a renderer/digital bridge from a private party in Canada listed on the Canadian Audiomart.  Today I received electric cable from Hong Kong. 

I have never had to pay a tariff.  Never.

I have sold to Canadian buyers and it has always been my understanding that Canadians have to pay tax, and brokerage fees unless they make arrangements, which are unavoidable.
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Thanks for your opinions. Others be careful buying from foreign countries  in the future.
I believe the tariff could be exclusive to equipment of Chinese manufacture due to the previous U.S. administrations trade war policies.

I bought a streamer from Hong Kong last year and it was held until I paid a tariff.
Yes, I believe so. My sister works import export for UPS and yeah a lot of things originating in China gets what they call the  T tax .
I just looked it up the company is based in HK. I believe the production is in China. 
UPS has been using a new system.  I don't know if this is a sub-contractor or new division.  Not only do they try to collect "legitimate" tarriffs, the fees involved are highway robbery.  I ship all of the time both ways across the border and only started experiencing this over the past year.  Calling UPS can be as impossible as calling the IRS.
If you keep calling, you might get the right person who will reduce the fees.  The other option is to tell the seller that you are stopping payment and they have to take the item back.  Offer to pay the return shipping to them and walk away.  This Canada-US thing is getting out of control.
I believe used items from Canada aren’t subject to tariff. But it’s based on the country of origin and this made in China component has an outrageously high tax due to our trade relationship.

I purchased a used dac from Canada, built in UK, and the VAT was about $40 (shipped UPS).

As someone in Canada who frequently imports used gear from the US/EU, I’m always tagged with duties. Make sure you ask the seller to report a "fair value" for the item you are importing .. if you get my drift.