I don't disagree with any of that Neil and the two kits you mention are indeed a waste of space. I also agree with Brian that paying a high price doesn't necessarily get you top quality goods, there is always someone who is happy to charge top dollar for rubbish.
Nonetheless, my point is that some retail suppliers pay more attention to quality control than others and if you buy cheap kits from suppliers who are more concerned with price than quality then there is a greater risk that what you get will be rubbish.
Buy £2 slimlines from eBay and you might be lucky, they might have come from the factory that was producing round components that fit in the tubes that week or you might be less lucky and get the components that result in a cock-eyed pen or need gluing into the tube.
Its all a bit of a lottery, but sticking with suppliers you trust is less likely to result in disappointment. If you know that the JG's from a particular supplier are crap then stop buying them and if they are happy to sell you crap JG's then why would you trust anything else they sell. It's not rocket science.