Your complaint about the shipping time is fine, but you cannot fault someone for charging $4.00 for shipping when you see it only 'cost' them $1.10. I've had this discussion before, and it is very annoying. Frankly, if you didn't want to pay $4.00 for shipping, then you shouldn't have bid on it. Also, is the postmark on the package correct? Sept. 10? If it is, then I'm not sure what your complaint is...If it says Sept. 10 and he said he shipped it on Sept. 2, then maybe the Post Office (If that's who it came from) held it for 8 days, which isn't unlike them at all. I'm going through the same type of situation with a buyer, and I have explained I cannot control the shipping company, whether it be USPS or FedEx or UPS or DHL or any others. I even provided a receipt to the person showing I didn't print my own date and that it did ship out on time, but they still think it's my fault.
If you are going to blame someone, support your claim with evidence.
$4.00 shipping...packing probably cost around $1.00, postage was $1.10. If they are not near a post office like myself, then gas is probably $1.80 - $2.50/gallon, and 30 miles round trip in a 30mpg car is $1.80 - $2.50. I won't take into account wear and tear or depreciation, which on a well maintained car like my Mazda is $0.02 to $0.05 per mile (depending on highway or city). So, the total would be...$4.25 (average price of gas at $2.15). Seems to me, you got by with a decent shipping charge.
Yeah yeah, you could say he had to ship out 10 other packages that day as well, so the actual cost for your package is less, being included with all the others...but, perhaps he made a special trip, like I do, just to get the package out in a timely manner.
So, if you're upset with his shipping process, then state your claim with facts.