Earlier quoted context omitted.
realistically speaking, it is likely not possible to deliver envelop from China at 75c cost, its likely someone else is paying for your 75c envelops (like taxpayers through subsidies).
You've been downvoted, but you are 100% correct. It is the result of the UPU treaty: https://www.weforum.org/stories/2018/10/us-withdrawing-144-y...
Here in Australia I can order a $10 (AUD) item from aliexpress and get free shipping from China. But as a consumer or small busines, if I want to send anything bigger than a letter within Australia it's likely to cost me way more than $10 just for the postage.
It doesn't make sense and it must distort retail trade in China's favour. I'm honestly not surprised the US withdrew from that treaty, I think it needs reworking.