You don't necessarily need a lot of cash for lightweight gear. For instance, Campmor has their Campmor brand down sleeping bag, often recommended to those on a budget, for $120 in regular, $130 for long. It weighs 2 lbs. 4 oz. in regular, 2 lbs. 6 oz. in long. It's listed at 20*F, although most consider it more like a 25-30*F bag. With insulating clothing worn inside, it should be just fine for frosty nights in the "Bob." In other words, the OP will have a sleeping bag that's adequate for the conditions at half the weight he listed for an inadequate 40*F bag. Use a 2-mil trash compactor bag (if you can find an unscented brand!) or a cut-down 2-mil contractor's trash bag as a pack liner to keep everything (including the sleeping bag) dry, and you won't even need a stuff sack. Use a "candy cane" closure--twist the top and fold it over on itself before tying it shut--to keep water from getting inside.

Lots of ideas for saving $ here and in the last chapter of this online book.

Admittedly, paring the last few ounces off an already very lightweight gear list often does require a lot of $$$, but you can get down to a 15-17 lb. base weight without spending any more money than you would for heavy gear.

And as far as safety goes, trying to get over rough trails with such heavy packs will certainly result in injuries! It will also make sure that the participants part enemies (or at least no longer friends) and that they never backpack again!

My recommendations are based on an intimate knowledge of weather in the northern Rockies. I grew up there, spending most of July and August high up near or above timberline, and have been back many times since. That's why I recommended warmer sleeping bags. However, the OP is going to Montana's Bob Marshall Wilderness in July, not to Colorado's Collegiate Peaks in October.