When buying from Ebay there is a fundamental issue you must understand, transaction is not complete until you the buyer receive the goods, not when seller sends the goods.
Sellers offering insurance is only saving the seller money, it is seller's responsibility that you receive the goods; this applies to all items regardless whether seller in their listing explicitly states it is buyer's responsibility for insurance.
Also, sellers in their listing including they reserve all rights to cancel the auction. If there are bids and item has less than 24 hours remaining, seller cannot cancel auction. If item is cancelled, write to Ebay and seller's account will be suspended.
Similarly, if you're returning a product to seller, make sure you send it via a service that allows tracking and signature, it is your responsibility to ensure seller receives the returned product.
Have a read of this if you've time.