You might be onto something. I have a $50 thin plywood cajon (made by a relatively local joint called DrumBox Percussion) and a $200 Toca cajon which I think is made of oak. The Toca looks beautiful and has a crisper sound but feels too stiff. The DrumBox does sound a bit cheaper but has more oomph in the bass sound and is more playable, and also more light and portable.I think you sort of need the thin sandwiched material to get a good sound from it. There needs to be a "membrane" for it to be a drum. The more solid your materials most likely the less sound/projection you'll get. You want a balance between too hard which is echo-ey to too soft which will break and produce a light sound.