If the optional insurance fee is for the Post Office fees, I wouldn't bother with it. The PO only pays for lost packages, and that rarely happens. Very rarely. They do not pay for live plants due to damage, or due to length of time in transit.
This is my understanding.
I never insure plants, figure it's cheaper to resend than to pay for something that might get lost, when I've never had anything get lost.
This may be a private insurance with the seller, though. I know Schreiners Irises, for ex, will guarantee your plants to live for a set amount, but if it's to cover PO fees, I wouldn't.
