Everybody's numbers don't count the time they'll need to spend in line at the PO because it is an international shipment. Because it is light, they could drop it in the mail for domestic mail, but to send it to you they'd actually have to show up at the PO, fill out forms, and stand in line to ship your package. They're probably charging you for their time (ie the handling).

I've never really understood your fondness for "bargains" and eBay, personally. Is it even a legal license for the software?