This is the chipboard I use to make my pattern pieces. It's become a necessity in my sewing life, and I can only find it in massive boxes of 500 sheets, so I sell the extra in my etsy shop. I use a lot chipboard, but it would still probably take a year or two to use a box this large!
If you plan to make multiples of something, taping or gluing the paper pattern pieces to chipboard makes it easy to trace many of the same piece over and over. Punch a hole in the pattern piece and then you can hang them up on the wall where they are easy to see, but out of the way.
These legal size chipboard pieces are great for using to make some larger pieces too. You can join multiple sheets with some tape.
I did this for the body pieces for the Grocery Bag and it makes it super simple to just grab the chipboard pattern pieces and quickly trace the fabric pieces. Having these sturdy pieces has definitely helped me increase my sewing output.