I usually pack it up as I would any other mail (ie bubble wrap etc) and send it insured which is $9 for the first $100, $3 for every $100 thereafter on top of your normal postage charge. This is also fine for Paypal as proof of postage as you retain a carbon copy
for just 1 card in a bubble mailer mine is usually about $7-$8 for registered overseas mail, but it will be more for you scotty as you are sending it from tassie, which will probably be a bit more in postage charges.
i am pretty sure it is a max of about $3 for an extra $100 insurance
What else can I tell you?, I am not big fan of handling fee,petrol..ect, I think $16.50 for a $100-200 card is reasonable, coz they paid via paypal, without insured and registered, just
too difficult for both buyer and seller.
So is it a set fee/envelope or just the rate that it ends up being after you've got the envelope, weight, and charges (with insurance & registration - parcel).