Interesting discussion, and an excellent idea! Would it perhaps be a good idea to cross-reference this thread in the Beginners' section?
For more ideas, there are some articles, gear lists and forum posts on BackpackingLight about items for Scouts, specifically geared to Philmont. Fortunately, these are all free to non-BPL members. These are referenced on Mark Verber's website, which also lists inexpensive possibilities for each gear item in his "preferred gear" section.
There's also an interesting "ultralight, ultracheap" gear list on the Gossamer Gear website, in their gear list section. I suspect this is several years old, so the prices will need updating.
It is quite possible to get nearly all one's clothing, and a number of gear items, from thrift stores for next to nothing. It may take a number of visits, though.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey