Where do you find affordable maple and walnut for a cutting board?

First check whether those prices are for rough lumber or boards that are already surfaced and squared. A 1.5 by 4 by 48 inch piece is 2 board feet by volume, but the final usable size can be smaller after milling. Ask local hardwood dealers or sawmills what they charge by the board foot, and compare the actual dimensions and condition, not just the sticker price. Short pieces can be surprisingly expensive because they’re sold as project-ready stock.

For a small board, I’d ask nearby cabinet or furniture shops if they have clean offcuts. A box of scraps can be much cheaper than buying full boards, and you may only need short lengths. Also check local lumberyards and sawmills for cutoff bins. Make sure the pieces are dry and thick enough to flatten, and skip anything with paint, treatment, or an unknown finish for a food-use project.

There’s no guarantee that making one will beat the price of a finished cutting board. You’re paying for the lumber, waste, and the work, and small quantities aren’t always sold cheaply. If the fun is making it as a gift, that may be fine. If you mainly want to lower the material bill, consider a smaller board, using more of one wood, or designing around whatever suitable offcuts you can find.