Your magazines could probably be mailed at Letter rates. If each shipment weighed 499grams, the maximum for Canada would be $5.47 and for the USA would be $11.14.
Most magazines would weigh less and cost less.
BUT
Letter post does not included tracking, which is one of the few Seller Protections we have.
On the other hand, your buyer is likely to be an older guy, feeling nostalgic and a pretty easy going person.
The protection you get from tracking is the ability to disprove a false Not Received Dispute.
And in that category those are likely to be rare.
So using tracking is as much an emotional decision as an economic one.
Tracked packages-- well within Canada you could Register* a Letter rate item for $9.75 plus the postage.
And you can use this to work out the cost of sending by Regular Parcel within Canada.
https://www.canadapost.ca/cpotools/apps/far/business/findARate?execution=e1s1
I hope you were sitting down when you read that.
You can ship to the USA (still under 500gr) for $20.10. (cheapest tracked packet is $14.42 for a mere 100gr.)
I'm going to use the tracking system, but I don't know if I should insure them or not: some of them might be worth $200 (!!!) Does Canada Post do that?
Canada Post does insure. It's not all that great if you have to claim and not really all that useful since the postal system is very good at its job.
Very generally, here's my advice.
Start with the ones that have the lowest values. Better to mess up a low value sale than a high value one. And you will mess up once or twice. There is a learning curve.
Do I have to pay any kind of customs fee or taxes when I ship?
No. Duty and sales taxes are paid by the buyer/importer.
Should I declare the value to the buyer (who might pay a lot because it's a collectible) or the value to the average person (who would throw it in the recycling bin?)
The value is what the buyer paid for it. Nothing more or less.
The shipping label will ask you for the contents of the package (automatic if you buy it through Paypal) .
There is a Harmonized Sales Code now which is international - magazines are 4902.90
https://www.canadapost.ca/cpotools/apps/wtz/business/findHsCode?execution=e1s1
US residents have an $800US duty free allowance. I hope some of your sales are high enough to make the customer pay duty!
*Registration stops tracking at the border. Don't use it internationally.
