I'll try to shed some light on the Amazon availability, with the caveat that I don't fully understand it either:
Drop has the tents at a USA warehouse and lists them on Amazon USA where they can control the pricing and sort of control the distribution. There are three ways you can get the item internationally:
1) Drop can choose to fulfill the orders to international customers from their USA warehouse. This works and is within their control, but international shipping is expensive because they're mailing individual items all over the world (rather than larger shipments). They did a small trial of this last week with 10 tents and it works but shipping is around $50 USD.
2) Drop can hope Amazon USA selects the item for their export program, which would let it ship from Amazon USA all over the world but with the shipping handled by Amazon rather than Drop. Amazon selectively enables international shipping for items they think are popular enough where Drop can't just turn that on. If the tents are selected for that program then suddenly people all over the world can order and it's cheaper shipping because it's going as part of a larger batch. Someone in Australia buys from Amazon USA and the tent gets shipped on a pallet with a bunch of other stuff going to Australia.
3) Amazon can choose to list the items on their various international sites like Amazon Australia. Drop also doesn't have control over this since Amazon's computers have to decide if they want to stock it or not. That's why it's intermittently available on Amazon Australia. If Drop keeps it consistently in stock then it probably would remain in stock on Amazon Australia, but when it sells out and then returns, it can take Amazon a few weeks to realize it's popular enough that it's worth stocking. That's been an issue with the 2P where it's out of stock and then suddenly available in brief bursts. When Amazon does list it on their international sites they have control over the pricing because they are essentially buying the stock from Drop and selling it. Usually the price is pretty much the same as on Amazon USA but sometimes funny things happen. It could be higher due too import tariffs and taxes, or just Amazon doing something funny. Recently the 1P was very expensive ($5xx AUD) but seems to be fixed now ($3xx AUD).
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As mentioned, Drop recently did a test of 10 X-Mid 1P where they shipped it internationally from the USA warehouse. Simple to do but expensive shipping ($50-$60).
Fortunately, in the last day or two Amazon figured out that these tents are popular so they have added the 1P to their international export program. So now Australians can buy directly from Amazon USA without using a re-shipping company and with more affordable shipping. It looks like you'd pay $220 USD + $35 shipping and then they're not taking an import fee deposit, so you'd probably have a bill for whatever tax Australia charges when it arrives (unless there is none).
Screenshot here:
https://i.imgur.com/oWq892H.pngAs for Amazon Australia, as mentioned Drop can't control if the product appears here nor the price, but usually Amazon will figure out that's it's popular enough to stock once it's been selling in the USA for a bit. I'm not sure why they had it for a really high price recently but it looks like they figured that out now. I see it listed for $316 AUD which looks like a good price because that's $245 USD and presumably has free shipping. So it's good to see they have this sorted out and that's probably the best option for Australians now, but if it did go up in price or become unavailable it would hopefully still be available for export from Amazon USA, and failing that, Drop could re-enable international shipping from their warehouse for a bit higher cost.
As for the X-Mid 2P, it takes Amazon a while to figure all of this out. They want to see sustained sales before they start stocking it all over the world. So when the X-Mid 2P re-appears on Amazon USA when Drop releases the next batch (likely next week) it probably won't be in Amazon's export program, and it's hard to say if Amazon will list it on their Australian site. So I think Drop is going to enable their own more expensive international shipping for that launch (but I'm not 100% sure so I can't promise this) so that everyone can order from Amazon USA, and then if it is in their export program or Amazon Australia then it'll also be available via those routes and for a bit less.