I've found that in Aust as well. I did question a seller when a $20 hard-to-get coin ($5AUD postal charge) turned up in a standard envelope with a 50 cent(standard letter stamp). I received the same answer as Mike (how difficult it was to post an article etc etc).
Additionally, before I bid on an article, I contact the seller to verify if they will register the parcel (its an additional $2.35 but must be signed for and if lost can be traced). If no to register I don't bid. Post times here are usually 3-5 days.
I have purchased coins and early American Country music from US based
ebay sellers and record sellers and have been delighted with the service (post was lightening quick).