Just throwing it out there. I ran by HD the other day to look at the 1/2 x 23-1/4 in. x 4 ft. Edge-Glued Board and found them on clearance for $6 a piece. They are normally $25. Lets just say my local HD does not have them in stock anymore and they are sitting comfortably in my garage. This might be a local thing (Anaheim CA) but it might be worth it to look. They carve up pretty good for signs.
I am going to check the surrounding stores today and pick up a few more if I can.