I am not sure how you were able to start a post im PLTek, llc forum, lol,...
I actually include 2 uppipe gaskets with my flow uppipe as a package 215USD shipped. If you get COBB or other uppipes, you can get all the gaskets you need in the gaskets sub-section which is in the exhaust section. you can either just get the top and bottom uppipe gasket for a full kit which includes all the gaskets that you should really change when you change the uppipe, Here is the link:
In terms of shipping via USPS, i have to use them to ship small things worth under 100USD where 5 bucks is a difference between profit and loss. I hope that answers your questions.
Thank you for your continued support