I want to ship/mail a beanie (aka knit cap) to someone in Australia. The USPS appears to only have fairly expensive options that exceed the value of the item - a flat rate padded envelope is $43, or a small box is $20. FedEx, UPS, and DHL are absurdly more expensive. 
Are there cheaper options? There have to be cheaper ways if I can buy a $25 thing on eBay and have it mailed from China to the US for free, right?
Fill a container. Apparently shippers need more containers for export from Australia than they are getting from imports. (At least this was the case during the pandemic - $500 to ship a 40’ container from California to Australia while it was $7,000 to ship the same container from China to California). If you ship 500,000 hats that’s just a tenth of a penny each in shipping!
ETA - In all seriousness, for a single item, the post office is your best bet. Big companies combine their orders in bundles and are broken up into individual mailings in the country of delivery. That’s how we get small orders shipped from China so cheap.
I think this is one of those situations where we’ve been spoiled rotten by bulk international shipping.
When you think about precisely what’s being accomplished, twenty bucks to mail a hat to the other side of the planet is pretty remarkable.
What’s worked for people I know is to find someone who is traveling to the country in question and giving them the thing to take and then ship via domestic post.
International postal rates are weird. Here is a Planet Money episode that explains about the group that sets the rates. As discussed in the episode, it can be cheaper to mail from China to the US, than within a city in the US. If I remember correctly it isn’t paid per item, so the Australian post doesn’t see any of the $43 you pay to the USPS, but then at the end of the year the US and Australian postal services will pay each other a lump sum for the estimate of the number of packages that originated on one, but were delivered by the other.
20 years ago or so there were some pretty cheap international parcel options from the USPS, but those have been gone for a very long time. I had to ship a very small box to Europe recently, and the best I could do was USPS for $35 or so, which was even cheaper than the business rates we get on the various private couriers.
Can you vaccum seal it enough so it meets letter mail dimensions?
For sale-Crystal Vase*
*Some assembly required
Look at Pirate Ship’s Simple Export Rate:
Basically you mail it to their forwarder and they re-ship it to Australia. Their half pound rate is $11.99 to Australia [this includes both shipping it to their forwarder and them forwarding it].
Note to activate this you need to chat with customer service and they will immediately add it. There are no other charges to use this service other than the specified postal rate.
Shipping from China is cheap because it is unimaginably common, and in logistics economies of scale are substantial. The US - Australia route is tiny in comparison, and costs increase accordingly.
Sure prices were cheap but it took one to three months to arrive. When the USPS stopped surface mail to Australia the price started to slowly climb, Around twenty to thirty bucks is the normal nowadays for a small parcel.