As the troop leader, you are in charge of running the troop physically as well as financially. Even though you may have a treasurer who does the paperwork for you, the final decision on how the money is spent rests on your shoulders.
One of the reasons I started this blog is to help leaders in all areas of troop leadership. If you do big cookie sales (I do not) then your cash flow is better than mine.
I prefer to use as little money as possible on the crafts. The internet is full of great websites for scout leaders and I use them for almost all of my craft ideas. Many of these crafts use many common objects around the house like paper bags and paper tubes that are free!
If I do need materials for a craft, then I go to the craft store with a coupon and buy what we need. I will take another person or two so I can use more than one coupon. Since I am paying cash, I do not use the troop check book to get the items tax free. I am saving at least 40-50% percent on each item, I do not mind paying the tax (and imagine the people behind me when I am writing checks for two and three dollars multiple times!).
My favorite crafts are the ones that use a printable, markers, and some glue! Check out my Daisy Girl Scout blog for many different craft ideas for those on a budget.