Ya but if the buyer paid via paypal or paid via credit card, you are going to loose regardless if you the buyer chose to pay for insurance or not; paypal will favor the buyer.
Its the seller job to protect themselves, not the buyer, all the buyer has to do is claim they didn't receive something they paid for and that’s it. Read the paypal buyer and seller protection guidelines.
In other words even if you go to paypal saying but he didn't pay for insurance; paypal will say "So that means you can't get your money back from usps, but you still have to pay your buyer back"
Also you can take your local USPS to small claims court if the don't pay you, once again, just because they claim you didn't have insurance its still there responsibility to deliver the package, if they fail to do so, and you can prove what the item was worth, you can get them to pay you back; you just have to twist the arm harder
