I have been getting about 1/400 "lost" which I find quite remarkable. When I first started it was quite a bit higher for some reason.

Also I have been buying stamps on ebay at about 75% face value to "self insure". I also register items at my own cost if I feel the need and hand my mail over the counter, if that makes any difference I don't know.

For lost items I originally offered a resend or refund but now I just do a resend (I only ever had one person want a refund in all my time on ebay), confirming the address details with the customer, and then sometimes block them if I think something is up.