When selling items online it is of course necessary to ship those items. Depending on their value it can be a tough decision whether or not to insure the package.
I recently shipped a $2,000+ jewelry package. You better believe I insured that puppy and it cost me over $35 to ship. Yes that is a lot of money just for shipping but the peace of mind it offered me was worth the cost. It arrived safely and with no issues. I'm sure if I had shipped it with no insurance it would have done the same. But I would not have been able to sleep until it arrived.
Generally, if an item is over $100 I will opt for insurance. But the fees can add up fast. Sometimes, I skip the insurance, which makes me nervous but generally there are no issues. If I insured every single item I shipped I'd increase my shipping fees and cut into my meager profit margin (because trust me, I do not price my stuff correctly LOL).
Another issue to consider though is tracking your package. If you work with Paypal for your payments you can add free delivery confirmation if you ship Priority. This is my standard shipping method. Plus you get a discounted rate if you print your label online. Just remember, if anyone disputes their order via Paypal, you as the shipper have to have proof that you shipped that item out or Paypal will side with the customer and refund their money from your account.
My advice - if an item is irreplaceable, even if it only costs $20, insure it. It can't hurt and will give you more peace of mind. If it is something you can replace easily and it doesn't cost too much go with Delivery Confirmation instead and save the money.