Earlier quoted context omitted.
I think the primary barrier here is that, while you can assume based on IP/Locale, you don't entirely know where the customer intends on shipping the product, and therefore rates fluctuate. It would be great to allow customers to estimate shipping as soon as possible, rather than just before clicking the "give us money" button.
Also, you want to present the same price to all customers.
People already understand the price of an object vs the cost of sending that object somewhere in the world. Everyone understands $100 shoes with a shipping fee, not $105-$130 shoes that shape-shift depending on where the person lives that opens the link.