I also started with Mianne as my base, and then things spiraled out of control! Plywood has come down, but not nearly where it was two years ago. I bought my 1/2" Baltic Birch multi-ply 5 x 5 sheets for less than $24/ea, this is furniture grade 11 ply panels. I'm sure it's still way more than that now. However, my feeling is not to skimp on the base as I'm putting thousands of dollars worth of track and switches on top, then running thousands more worth of trains on it! I love the rigidity of the multi-ply, warping is simply something that ain't gonna' happen here!