1. Demonstratively, if there is a workshop, carry in your full throttle traditional backpack. Inside the pack goes the fully equipped lightweight pack and gear along with as much traditional gear you can also fit in. Have folks try the full load on for size then match the items, focusing on the "big three plus footwear" item for item and then compare the two.
2, Advising, "do not buy anything without checking with somebody first" Advise to rent from shops, even if it is heavy, borrow whenever you can from lightweight folks, buy top quality light weight gear only. Post needs here and on other boards. Perhaps shop for one generation removed gear at closeouts, etc., or sierratradingpost.com and the like.
Buying cheap (as opposed to inexpensive) gear is something that I thing has got to be discouraged. It is like golfing, and whether you should buy a cheap set of clubs or good ones. If you buy the cheap stuff you are wasting whatever money is spent on that gear. You will either not like the "game" and not use it again, or you will love the game and immediately start upgrading to better materials.
3. On the trail, if you bring a novice, make sure that there is one experienced person for each novice. Comparing the gear you have with the traditional gear the person has will illuminate the light to lightness