Export shipping small items from China

Hi, I hope there would be some uncynical answers (if any) but I’ve always wondered how does the Chinese companies (in China) ship stuff overseas? I’m not talking about containers (FCL/LCL) but more of small items from Aliexpress that provides free shipping regardless of quantities ordered. I know that they do charge slightly higher than local market Taobao rates (but not all as I compared prices with some electronics that I can get from Taobao and my friend from Aliexpress and at time it’s even cheaper to buy it from Ali, discounting the 3 weeks wait vs. a few days for me) I know that sending stuff from the post office would likely be the cheapest way, however I realise that they can be quite picky with what you can send (no metals objects etc.) and it wasn’t very cheap while another way would be to ship from Shanghai to a 3rd party shipper who would like have a warehouse in Guangdong who would then bulk ship to your country of choice (slow and expensive with a min. of 1kg), but is there a better way to do this? The only thing I can think of is that these companies might perhaps be located in some trade free zone that have more “flexible” post offices and also contracts with shipping companies as well as special guanxi. TL:DR – How companies ship stuff on Aliexpress to individual buyers for little to no cost. Anybody can shed some light here? Thanks in advance.