Would you be willing to drive to Joliet or McHenry? Both these cities near Chicago have a
Roofing Insulation and Supply warehouses. They generally deal with large contracts but will sell product to individuals. I had their Indianapolis location special order me a case of 703 and it came out to $.96/ft2. While I was standing in the warehouse I saw that they normally had Roxul AFBs and Rockboard 40 in stock, both of which can be used for DIY panels.
Another option is to look at the various ceiling tiles available at you locale big box store. Certain types use ridged fiberglass as their backing martial, these are usually meant for use in open plan office spaces. I’ve found that this fiberglass backing can have a range of densities that are equivalent to 701 to 705. Just last week I saw some 2x2 tiles at Menards for $2 each they had a 701 or 703 equivalent backing. The caveat with using this material is that you must glue together multiple pieces to get an appropriate thickness for broadband absorbers.
The pink fluffy stuff can be use for corner style bass traps, if compressed sufficiently. As a panel it would probably be okay for mids and highs, if it were compressed into a frame and you made panels that were at least 6in thick, but thicker would be better.
