I recently bought a sheet of 3/4" hardwood veneered “plywood”. I thought that I was really getting old because it kicked my butt to unload it, move it to the shop and set up on the workbench to begin breaking it down. Then I realized that it had two 1/4" plies that were MDF. No wonder the thing was so heavy. I felt better about my physical condition after the revelation. :)
-- Art