That looks like a lot of fun. For how simple it is, it seems about on the level of complexity of the sort of thing you could buy at Harbor Freight for about a hundred dollars. If it were that easy, why don't they sell these at Harbor Freight? Is making a reliable turbojet actually harder than it looks, or is there just no market for a small household turbojet engines?

I'm not sure what I'd use one for, other than maybe as a sort of blowtorch.