Regarding the inexpensive shipping on items from China, that goes back a long way, for almost a hundred years, through the Universal Postal Union, international mail within a certain weight, was transferred for free among the nations, then in 1969 they had a brilliant idea to actually add some money in there, on smaller nations, and charge less for the more developed countries (like the US). It was a really strange setup, but increased volumes of mail, offset the costs (in theory).
Anyhow, when eCommerce started getting prevalent, the United States Postal Service and China Post, entered into an agreement that allowed sellers to use what are known as "e-packets", for items up to 4 pounds, 4 ounces. It was great for China, because it was stupid inexpensive, not so much for mail to China though, as it was still quite expensive. The USPS justified it, because it added almost 26 million in revenue for the first year. Yet, for some reason, the folks in charge of running the business of the post office, don't understand that if you increase revenue by getting 26 million more in, but it costs you 29 million to do it, you have actually lost money.
Anyway, in 2018, the president of the United States brought this up, the disparity of pricing charged and asked why? Congress is looking into it, and it looks like the e-packet trade will be done away with, at least at the pennies on the dollar cost that is enjoyed today.
There are quite a few good articles about it, yet the direct result is that the USPS is looking at how to fill in the hole, and increasing service costs always seems to be the answer, never mind, not increasing service itself.
Aside of all of that, the more you ship, the less expensive your shipping is, the shipping companies will factor the volume in, and offer you better pricing based on that.
Back on another discussion, regarding paypal fees, I had mentioned that you can use paypal postage printing service, which is actually about 5% or more less than what you pay at USPS website, and 6 to 7% less than at the post office. Also, the 3% number that everyone throws around, regarding paypal fees, isn't exactly correct. If you sell an item, get paid for good and services, either factor that cost of payment processing in. I think that on fee processing I actually pay just around 2%, sometimes less. Then the postage savings helps to offset that in the end.
Just part of what I have learned doing e commerce since 1999. Ultimately though, USPS is pricing itself out of business.
https://www.uspsoig.gov/document/inbound-china-epacket-costing-methodology
https://www.theatlantic.com/technol...anges-terminal-dues-and-epacket-rates/573337/
