The cheapest service is USPS... Ask your uncle to try it via "USPS International Flat Rate Box", if all the things accumulate in that box the postage will be around $60.00 USD. Even with $500 of insurance it won't be more then $70.00.
And if not it can be shipped in its own box via USPS Express Mail International service with $500 of insurance, the postage will be around $110.00 USD... (based on 15 pounds of total shipping weight)
The customs duty on laptops and personal computers is 0% but there is/are other tax(es) though that need to be paid (not sure how much). In order to keep the taxes low the invoice value of the laptop should be kept as low as possible. But you'll have to be all prepared as they would have many other ways to ditch you up, since they don't only rely on the invoice value but also the market value of that product in Pakistan.
Now the choice is yours!!!