suggestions on signature confirmations selling on ebay

I am currently selling on ebay and just recently i have started to list higher priced items frequently at what price would some off you recommend to pay the little extra money for signature conformation on delivery incase of stole package or scammers saying they never received package on purchase. just wanted to get some info on what some people thought with years of experiance. i am starting to do to use signature conformation on all items over 100.00