This is my over 10 year old Dex build, it is awesome design and has served me so well as test platform and just fun to fly. I still have it.
And I was surprised to see thye are still available. Well why would they not, any other Dex flyers here.
Built this 10+ years ago when we needed a drone with a hollow centre. Frame cost maybe 20€ in materials and a few days to put together. Motors and electronics were the expensive part.
Back then it wasn't something you'd show off, everyone was building nice-looking carbon fibre quads. Maybe still the case, this one is functionality first: cheap, fast to make, easy to modify, and honestly flies better than a lot of the pretty ones. Excellent for prototyping.