I'm the only person I know, aside from via this forum, who would repurpose random junk for cooking on. For 90% of people, unless it came from a store, with directions, they would never think of using it.
Case in point: while on a camping / diving trip, I was cooking burgers over the fire, and realized I forgot to bring onions. I walked 10 steps away, picked some nice big chives, put them on a cutting board and sliced the bulbs up. My friends looked at me aghast. "What the hell are you putting on the burgers?!" was the kindest comment I got. Seriously, I had to explain that chives were a kind of wild onion. No one believed me - until they tried it.
Sure, baking steel bought in a store will be overpriced. Does that matter? Same damn people buy Pampered Chef products and think they're stylin.