If they're going 'soon', they're a little late to start thinking lightweight, but there are some distinct advantages you can bring.
A few of questions to ask:
Do I *really* need this item
As a group, how many widgets do we need / does everyone need their own (water purifier, eg)
What could happen if I don't take it
Is there a multifunction / dual use capability
Is there an alternative (sharing, something lighter, etc)
And, finally, Do I ***REALLY*** need it
They can get there by incrementally reducing weight, as few have a free Visa card to buy all new $$$ gear (much less the time to learn to use and appreciate it)
At this stage of the game, as most treks will start within the next month, I'd suggest comparisons of things like:
Flashlight:Your regular 8 oz flashlight vs 0.7 oz nano flashlight (one of these will last the entire trek if you don't leave it on overnight)
Tent: A 'lightweight' 2 man $39-49, 3 lb Sports Authority vs. Philmont issue 7-8 lb 2 man tent
Backpack: A G4 1+ lb backpack vs. a 5-7 lb other bag (note that just getting a G4 or other lightweight / lowcost bag doesn't work as well if you still try to stuff the heavy / bulky stuff in it.)
Layers: This is often a function of what they already have, but if they think about it, 3 layers can cover just about any weather likely for a July Philmont experience.
Sleeping bag: If it's not down, it gets pretty bulky and typically pounds heavier. I think this is one of the areas that is the biggest deals, and can make the most differences. Temperatures @ Philmont in July can range from 30's to 90's depending upon altitude.
Cooking: Between the heavier alcohol stoves they issue and the large cook sets, vs. lightweight approaches, you can save 10+ lbs pretty easy. We used canister Pocket Rockets, went through 2.5 lbs of canister gas, only took 2 pots and a spoon, adopting turkey bag cooking (major time and cleanup saver) Do you really need that 7 lb cast iron skillet as one Trek carried?
Crew Gear: Philmont is going to give them 'crew gear' that will take up more space and weight, so they need to lighten up before they get there.
Anyway, these are some the areas where we made the most difference last year. Our loaded packs ranged from 24 to 50 lbs, most others we saw ranged from 40 - 80 lbs. We're going again next year, and I expect all of our trek will be between 20 and 35 lbs. There does appear to be a correlation between weight and speed, and that translates into more free and setup time.
If the packs are beyond the 40 lbs range, they need to seriously look at what they are carrying and why, + possible alternatives, and sharing.
If they count ounces, they will save pounds. I spent a year getting ready, and went from a 51 lb pack to 24, and my knees really like it.
My 2 oz. worth.