If you ship through Paypal and use the USPS as the shipping service, insurance is also available. You select insurance and provide an estimated value. it then calculates the insurance cost and adds it into the final shipping cost. No need to go to the Post Office to use it. Also, a postage program like stamps.com will also let you purchase insurance without having to go to the Post Office.
"ShipCover" is eBay/PayPal's default insurance setting. You can select USPS insurance if desired, but I always take high ticket items directly to the P.O. and ship registered insured. It's worth the extra cost for peace of mind.
As Tom mentioned earlier, USPS Pub 122, "Customer Guide for Filing Domestic Insurance Claims or Registered Mail Inquiries says reasonable costs are payable for a number of things and then specifically states: Here's the link: http://about.usps.com/publications/pub122.pdf Look on pages 7 and 8.
I think that experience will tell you that mailing high ticket items can be risky unless you cover your butt... and you do that by going to the PO and shipping registered mail. EBay does not offer registered mail as an option, as this method has total accountability. Since most of the stuff I sell is junk, I've only had to do this once. Upload all info to your "my eBay selling" page and message the seller that a signature will be required.
Also note: for high $ items. It is far cheaper to send registered mail, and then insure it. I learned this some time ago. Ask the PO to compare the costs.