Call Illini Fire Equipment in Urbana, unless you already work for them (but it sounds like you don't) and just ask questions about the extinguisher business. They can probably give a fair assessment of the metal value and the work required to get it. Pressurized canisters are always a bear, especially if they number in the hypothetical hundreds, and Illinois' EPA does regulate them and forbid them from scrap without processing. My local extinguisher service takes them for free, remixes the halide, and scraps the cans. That doesn't make me any money but it's better than the "safety" guy destroying my livelihood because I'm stashing hazardous waste.