Well, I've just put my first TPU inner tube onto a bike. I got a fairly obvious staple like piece of metal stuck in a wide gravel tyre (48mm), and it was mild and warm weather, so thought I'd try one of the TPU ones I was carrying. They're packaged as RideNow but Amazon sells them from "Cyclami Ltd".
The price seems fairly typical for cheap(ish) TPU tubes on Amazon, £25 for 2 when I bought them, but have gone up by £1 now. They're 45g each, but I suspect that's simply because they're quite large inner tubes, for larger tyres. A pack of two was still about half the size on one traditional inner tube!
They were a little fiddly to get on, but I think that was just because the tyres are wider than most of my bikes and I didn't inflate them enough to position them well on the rim. Once I put a touch more air in them, they stayed in place more easily and worked OK.
Now we just have to wait, and see what their performance is like.