So USPS pricing does not make sense
Tell that to their pensioners, and healthcare provider. It's their healthcare and pension costs that is out of control and that's why USPS is in the deep hellhole it is right now.
And their only solution to their out-of-control costs problem is to try increasing revenue by raising rates for all of us.
Now, as to competing with HK and Chinese sellers.... you can't. Forget about it. You'll always lose.
They can get their parts, labor costs and shipping costs cheap cheap cheap!!!... even if you buy your parts in bulk.
The only way you can compete is by designing and producing innovative products that they CANNOT copy... well, at least legally.... i.e. don't give them permission to copy it.
In other words, OPEN SOURCE HARDWARE is a big freaking welcome gate and permission slip for Chinese and HK business to copy copy copy everything, produce it, and sell it far cheaper than you can ever imagine/produce by yourself here in the US.
So here you are, designing hardware and writing software and releasing it as open source hardware, and they'll be the ones benefiting and reaping the rewards... not you. They'll be the ones making the sale, not you.... and you can't do anything about it since well, you said it was open source.