I'm more suspecting it's fairly heavily subsidised by the government as a means to break Amazon in China and get an inroads in elsewhere - I'm expecting prices to increase when it's gotten a hold on the market.

I wondered about them as well, so ordered some random stuff a shortish while back.
I picked a bit of a random selection to cover as wide a range as I could with a few items.
This is what I bought as a test, took about a month to turn up.


Taking them in order
The motion sensor LED lights are pretty cheap and nasty looking - but I got them to use to backlight some cupboards when you open them, so they work great for that purpose, not sure how often I'll need to recharge the batteries, but they came with a sticky back steel and magnet combo, so easy to remove so you don't need to plug a usb cable in in situ.
    They look pretty crappy, but work well & for what they cost, micro USB instead of C for charge so this is definitely some left over stock, stuck in a warehouse, being sold off on the cheap.
I'll call it a cautious win, needs to be put out of sight, but where the sensors will detect movement, so a bit iffy.

The saddle square was, frankly, very nice - I only got this to see how the various marking tools would be, I'll probably get some others based on this one. 
Definitely a win.

The monocular, well enough made, lens seemed good, focus adjustment & anodised aluminium build - I thought I would be able to vary the magnification but couldn't (might just be me, but I've never seen binoculars or similar that couldn't). Small enough that I'll chuck it in the dog walking bag and check it out next time I'm up on the moors.
Cheaper than opera glasses, less useful than a Napoleonic telescope, so 50/50 - a win for the quality and a loss for having no particular use.
It works well for what it does, I guess, no idea who it is aimed at (probably the same people that the adverts at the back of comic books were aimed at, these will go great with your x-ray specs).

The drone was a fairly mixed bag - I wasn't expecting a lot for 3 & a half quid to be fair.
It claimed it was a special offer down from £30 odd quid, the phone app bit wanted access to make calls, so I used it on a sandboxed simless phone I use for testing, it worked fine with no phone access so a bit suss on that.
Saying that, it came with a (fairly crappy plastic) remote so it could be used without the cameras/app.
The instructions were in Chinese and what I'm calling optimistic English (i.e. translated from Chinese to English by a Hungarian goat farmer with no knowledge of technology), so took a bit of a play around to get the hang of, but the controller had couple of thumbsticks for up/down and direction, auto hover mode with 4 buttons to micro adjust drift, 5 buttons (1 of which beeps a lot) that I haven't worked out yet, and some anti crash sensors that I only found out how to activate after hitting the walls and floor a lot (probably should have tested it outside instead of in my shop).
If you are planning on smuggling drugs into a prison, this is a loss, no great lifting power, kinda hard to steer.
If you want to keep a small child quiet in a field for a while, this is a win - cheap and cheerful, comes with it's own remote and is moderately easy to control - the drone came with 3 rechargeable batteries (no idea on the runtime between charges) and the remote needs 3 AA batteries, so one of the few toys I've ever bought where it actually costs more to buy the batteries than the toy.

This ends my first thoughts on using Temu, mostly low end crap and also some decent stuff, pretty much like Amazon.
I ordered on the website and used PayPal to keep a bit of distance, so they have about as much information about me as my local takeaway.

From Crowie's point of view - I made a 1/12th scale mockup of my dining table and benches before I made them so SWMBO could agree to the build, but the final table is made of out 3x3 reclaimed railway sleepers so might not be the look you're after for the doll house. I may still have them somewhere, I was using the table as a coaster for awhile so it must be around somewhere.

Thinking about it - isn't making dollhouse a pretty close match to your skillset of making awesome scale modes?