It's not a good idea to play games with Canada Customs. "Adjusting" declared values is pretty normal with private sales, don't try it if you run a business though. Using "sample - no commercial value" is OK a few times, but CC will notice if a non-business is getting a lot of samples. Same with "warranty" no-value claims - they are keeping track of this stuff, and abuse will get their attention.
Basically they don't know what old used stuff is worth, but they know who is getting shipments. A pattern of oddball shipments to you will draw attention, and you'll have to justify all of them when they come calling. This is never fun. And the penalties for fraud and/or smuggling are definitely not in the "fun" category.
Postal service is absolutely best. The postal customs guys are either the laziest or the nicest, stuff often gets through totally free. You usually get dinged for GST on declared value, and there's some duty on new stuff depending on country of origin - if it's USA origin there's no duty.
UPS, Fedex, DHL, whatever... avoid whenever possible. Just when you're smiling about not paying duty and tax, you get a bill for both plus $40.00 or so for "processing" if the delivery guy didn't collect it on delivery. You can specify a customs broker to process the shipment but realistically you won't get it much cheaper. If you ignore their bill you won't be able to ship using that service again (you can take stuff to their depot but they will not pick up at your address), any duty/tax/processing charges will forever be COD on deliveries, plus you'll get endless pestering from a collection agency.