This assumes that the shipping rates will be the same anywhere that they serve. That's usually an incorrect assumption. This format allows for variations in the shipping while keeping the same unit price.

Edit: Although, I am confused that they send me through the Paypal service before collecting my shipping address. Are they actually quoting me a price based on IP geolocation? That's kind of a dumb assumption; I send half of my traffic through a private VPN. I could probably save quite a bit of money by switching to U.S. East coast server for the payment processing.