It always kinds of scares me when the post office clerk asks "do you want to insure this?"
my immediate thought is "Why, were you intending to mishandle it?"
Seriously, it is worth the extra cost of insuring it.
I'm not sure how much one can recover for a quilt without an appraisal beyond "reasonable" cost for the materials.
I received a piece of antique Croesus glass that was broken - all the other pieces in the box arrived intact - and the postmaster wouldn't accept my word or the seller's word on the value. I had to provide a couple of sources - with pictures - of approximate value.
I had to bring in the item, the box and packing materials, the insurance thing that showed insurance had been purchased - neat trick when the seller had it and was several states away - "proof" that the item was worth what I said it was
Also, the clerk at one post office branch said I had to return the whole shipment to get anything done - then I went to the post office immediately over that one and was told I only had to submit the pieces from the one item.
Check into the post office insurance carefully before assuming that they will honor any $ amount one may assign to an item.
I think they should, but I don't know if they would.
Eventually, the claim was honored, but it took several months.