Question about Z app pricing and collectibles when shipping from Canada to US

I'm not sure about if this is the right place to ask about this. Please remove it if so.

I am trying to sell a collectible and send it from Canada to the States but I'm having a lot more issues doing it than the last time I shipped something (prior to the last strike).

The value if the item is quite high compared to it's original purchase price from the manufacturer, let's say $200 on the secondary market vs its $20 initial purchase price years ago.

I want to insure the package for the price the buyer is paying for it (to make sure we are both covered if it gets lost or something), but the Z app seems to value it at $20 using the picture AI thing for calculating the tariffs.

My question is, should I declare it as the buyer's value on the Z app for calculating the tariffs, or should I use the auto generated value? I don't want to do this wrong or break any laws or rules given the large difference in the tariff value vs the insured value of the package.

I talked to the staff at my local Canada post, and I talked to the customer support line and no one had a solid answer they were confident with.

Has anyone run into a similar situation?