Well, Lauan plywood, aka meranti plywood aka phillipine mahogany plywood is pretty easy to source. I have a local builders supply store that sells it for cheap and in full sheet sizes. It tends to come in a bit under 1/8”, about 0.10”. I posted about it at some point…
Here we go: Settings for 1/8" Meranti Lauan plywood
Worked out to about $0.37/sqft.