Now you know why I didn't open a book store on eBay. I was selling Antiquarians.
eBay seems to believe everyone should be like Amazon in terms of shipping costs, i.e. large scale and leveling would probably justify a $4.00 rate (media). Insurance isn't in that number, as far as I recall. It's just not a fair system for small scale sellers (IMO).
FYI...I believe lots, more than one, have a higher number for flat limit.
Also, calculated is probably a better method.
Danno