I would suggest that people take a pass on this poorly designed nozzle assembly. I could have created my own assembly in the plumbing section of a hardware store that would function the same for a quarter of the price. Nothing is to any standard, hose fittings are well designed to leak air into the system.. Plug and play this nozzle is not. If you need to extend the intake nozzle... buy it from them or good luck at one of the hardware stores. Perhaps this was intended to serve a certain market, but I suggest that the material will not last long and that the price will eventually seem like it was not the good deal we thought it to be. Better to get a metal nozzle that isn't as light, but will last. Consult Keene on modifying their 2" metal nozzle to reduce the weight somewhat, if that is your goal. Take note that the pump hose connection does not have a threaded attachment point.
So you haven't actually used or seen it? How do you know it's poorly designed? I guess anyone can say anything from the comfort of their keyboard.
I've used one of these nozzles (with their backpack dredge) and it works pretty good. The venturi creates a pretty strong jet with the recommended pump. It's designed to work with their goldibox dredge, not a gas powered dredge. That should be obvious though. I was impressed with how compact and light the nozzle was for a 2" nozzle. It's way lighter than anything you could make from PVC.
I've built my own own nozzles too from the plumbing section and there is no way you can buy anything off the shelf to make a nozzle as compact and lightweight as the goldibox nozzle. Especially one that requires no fittings or adapters. - no matter what the cost. With any DIY solution you're going to wind up with a much bigger, heavier and bulkier nozzle. it's only fair to make an apples to apples comparison and your DIY example is not a fair comparison. But to take it a step further.....
How is your DIY nozzle a 1/4 of the price? The real answer is it's not.
If you make your own nozzle: You can buy a pvc "Y" for $5 , a 180 degree bend for another $5 that will be much bulkier due to the size of the radius, then you have to buy the reducers and adapters and hose clamps (since your diy pvc nozzle is not made for a keene hose). That's another $15. How are you going to get it all to stay together? You will need PVC cement. Another $13. How much is gas to and from the hardware store? Another $5. So far, that's $43 for you to build a one off with no testing. A quarter of the price? Not even close. And how much is your time worth? Besides going to the store and getting all the pieces, you have to put it together. Again, your nozzle will be untested and unproven. Their nozzle is $65 delivered with free shipping and it works well.
I don't know what you mean about not being plug and play. The guy whose goldibox I got to use had the standard 1.25 and 2" keene hoses and they twisted right on the nozzle. There weren't any adapters required. The hoses twist on in one direction and they don't come off easily. You have to twist and pull pretty hard to get them off.
You were right that they are for a certain market. They are for prospectors who want to dredge in harder to access locations with much lighter gear or dredge unnoticed.
Sorry for the long post - I came across this and felt like I needed to share my experience and observations with the nozzle since I have actually used one.